解读思路
先看完Aspects.h头文件
再看AspectInfo类，AspectIdentifier，AspectsContainer，AspectTracker
再按照hook的主流程，add
remove
整体过了一遍，还是有点懵，不过比看这段代码之前强夺了。
源码
头文件，几乎每一句都有注释
//
// Aspects.h
// Aspects - A delightful, simple library for aspect oriented programming.
//
// Copyright (c) 2014 Peter Steinberger. Licensed under the MIT license.
//
#import <Foundation/Foundation.h>
typedef NS_OPTIONS(NSUInteger, AspectOptions) {
AspectPositionAfter = 0, /// Called after the original implementation (default)
AspectPositionInstead = 1, /// Will replace the original implementation.
AspectPositionBefore = 2, /// Called before the original implementation.
AspectOptionAutomaticRemoval = 1 << 3 /// Will remove the hook after the first execution.
};
/// Opaque Aspect Token that allows to deregister the hook.
@protocol AspectToken <NSObject>
/// Deregisters an aspect.
/// @return YES if deregistration is successful, otherwise NO.
- (BOOL)remove;
@end
/// The AspectInfo protocol is the first parameter of our block syntax.
@protocol AspectInfo <NSObject>
/// The instance that is currently hooked.
- (id)instance;
/// The original invocation of the hooked method.
- (NSInvocation *)originalInvocation;
/// All method arguments, boxed. This is lazily evaluated.
- (NSArray *)arguments;
@end
/**
Aspects uses Objective-C message forwarding to hook into messages. This will create some overhead. Don't add aspects to methods that are called a lot. Aspects is meant for view/controller code that is not called a 1000 times per second.
Adding aspects returns an opaque token which can be used to deregister again. All calls are thread safe.
*/
@interface NSObject (Aspects)
/// Adds a block of code before/instead/after the current `selector` for a specific class.
///
/// @param block Aspects replicates the type signature of the method being hooked.
/// The first parameter will be `id<AspectInfo>`, followed by all parameters of the method.
/// These parameters are optional and will be filled to match the block signature.
/// You can even use an empty block, or one that simple gets `id<AspectInfo>`.
///
/// @note Hooking static methods is not supported. //注意：Aspects是不支持hook 静态static方法的
/// @return A token which allows to later deregister the aspect.
+ (id<AspectToken>)aspect_hookSelector:(SEL)selector
withOptions:(AspectOptions)options
usingBlock:(id)block
error:(NSError **)error;
/// Adds a block of code before/instead/after the current `selector` for a specific instance.
- (id<AspectToken>)aspect_hookSelector:(SEL)selector
withOptions:(AspectOptions)options
usingBlock:(id)block
error:(NSError **)error;
@end
typedef NS_ENUM(NSUInteger, AspectErrorCode) {
AspectErrorSelectorBlacklisted, /// Selectors like release, retain, autorelease are blacklisted.
AspectErrorDoesNotRespondToSelector, /// Selector could not be found.
AspectErrorSelectorDeallocPosition, /// When hooking dealloc, only AspectPositionBefore is allowed.
AspectErrorSelectorAlreadyHookedInClassHierarchy, /// Statically hooking the same method in subclasses is not allowed.
AspectErrorFailedToAllocateClassPair, /// The runtime failed creating a class pair.
AspectErrorMissingBlockSignature, /// The block misses compile time signature info and can't be called.
AspectErrorIncompatibleBlockSignature, /// The block signature does not match the method or is too large.
AspectErrorRemoveObjectAlreadyDeallocated = 100 /// (for removing) The object hooked is already deallocated.
};
extern NSString *const AspectErrorDomain;
.mm 文件
//
// Aspects.m
// Aspects - A delightful, simple library for aspect oriented programming.
//
// Copyright (c) 2014 Peter Steinberger. Licensed under the MIT license.
//
#import "Aspects.h"
#import <libkern/OSAtomic.h>//为了下面用到的自旋锁
#import <objc/runtime.h>//使用runtime的必备头文件
#import <objc/message.h>//使用runtime的必备头文件
#define AspectLog(...)
//#define AspectLog(...) do { NSLog(__VA_ARGS__); }while(0)
#define AspectLogError(...) do { NSLog(__VA_ARGS__); }while(0)//哈哈，do while(0)
// Block internals.
typedef NS_OPTIONS(int, AspectBlockFlags) {
AspectBlockFlagsHasCopyDisposeHelpers = (1 << 25),//是否需要Copy和Dispose的Helpers，尚不清楚这个25，和下面的30是怎么知道的
AspectBlockFlagsHasSignature = (1 << 30)//是否需要方法签名Signature
};
//和系统的Block很类似，可以用Clang 把Block转换成结构体
/*
如下 2 个结构体 SampleA 和 SampleB 在内存上是完全一样的，原因是结构体本身并不带有任何额外的附加信息。
struct SampleA {
int a;
int b;
int c;
};
struct SampleB {
int a;
struct Part1 {
int b;
};
struct Part2 {
int c;
};
};
*/
typedef struct _AspectBlock {
__unused Class isa;
AspectBlockFlags flags;
__unused int reserved;
void (__unused *invoke)(struct _AspectBlock *block, ...);
struct {
unsigned long int reserved;
unsigned long int size;
// requires AspectBlockFlagsHasCopyDisposeHelpers
void (*copy)(void *dst, const void *src);
void (*dispose)(const void *);
// requires AspectBlockFlagsHasSignature
const char *signature;
const char *layout;
} *descriptor;
// imported variables
} *AspectBlockRef;
@interface AspectInfo : NSObject <AspectInfo>//继承自NSObject，遵循AspectInfo协议
- (id)initWithInstance:(__unsafe_unretained id)instance invocation:(NSInvocation *)invocation;//把外面传进来的实例instance，原始的invocation 保存到对应的成员变量中
@property (nonatomic, unsafe_unretained, readonly) id instance;
@property (nonatomic, strong, readonly) NSArray *arguments;
@property (nonatomic, strong, readonly) NSInvocation *originalInvocation;
@end
// Tracks a single aspect.
//传入的block打包成AspectIdentifier
@interface AspectIdentifier : NSObject
+ (instancetype)identifierWithSelector:(SEL)selector object:(id)object options:(AspectOptions)options block:(id)block error:(NSError **)error;
- (BOOL)invokeWithInfo:(id<AspectInfo>)info;
@property (nonatomic, assign) SEL selector;
@property (nonatomic, strong) id block;
@property (nonatomic, strong) NSMethodSignature *blockSignature;
@property (nonatomic, weak) id object;
@property (nonatomic, assign) AspectOptions options;
@end
// Tracks all aspects for an object/class.
@interface AspectsContainer : NSObject
- (void)addAspect:(AspectIdentifier *)aspect withOptions:(AspectOptions)injectPosition;
- (BOOL)removeAspect:(id)aspect;
- (BOOL)hasAspects;
//第一次简单用atomic修饰，原子性，不需要同步锁
@property (atomic, copy) NSArray *beforeAspects;
@property (atomic, copy) NSArray *insteadAspects;
@property (atomic, copy) NSArray *afterAspects;
@end
@interface AspectTracker : NSObject
- (id)initWithTrackedClass:(Class)trackedClass;
@property (nonatomic, strong) Class trackedClass;
@property (nonatomic, readonly) NSString *trackedClassName;
@property (nonatomic, strong) NSMutableSet *selectorNames;
@property (nonatomic, strong) NSMutableDictionary *selectorNamesToSubclassTrackers;
- (void)addSubclassTracker:(AspectTracker *)subclassTracker hookingSelectorName:(NSString *)selectorName;
- (void)removeSubclassTracker:(AspectTracker *)subclassTracker hookingSelectorName:(NSString *)selectorName;
- (BOOL)subclassHasHookedSelectorName:(NSString *)selectorName;
- (NSSet *)subclassTrackersHookingSelectorName:(NSString *)selectorName;
@end
@interface NSInvocation (Aspects)
//返回了一个数组，数组里面包含了当前invocation的所有参数
- (NSArray *)aspects_arguments;
@end
#define AspectPositionFilter 0x07
#define AspectError(errorCode, errorDescription) do { \
AspectLogError(@"Aspects: %@", errorDescription); \
if (error) { *error = [NSError errorWithDomain:AspectErrorDomain code:errorCode userInfo:@{NSLocalizedDescriptionKey: errorDescription}]; }}while(0)
NSString *const AspectErrorDomain = @"AspectErrorDomain";
static NSString *const AspectsSubclassSuffix = @"_Aspects_";
static NSString *const AspectsMessagePrefix = @"aspects_";
@implementation NSObject (Aspects)
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Public Aspects API
+ (id<AspectToken>)aspect_hookSelector:(SEL)selector
withOptions:(AspectOptions)options
usingBlock:(id)block
error:(NSError **)error {
return aspect_add((id)self, selector, options, block, error);
}
/// @return A token which allows to later deregister the aspect.
- (id<AspectToken>)aspect_hookSelector:(SEL)selector
withOptions:(AspectOptions)options
usingBlock:(id)block
error:(NSError **)error {
return aspect_add(self, selector, options, block, error);
}
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Private Helper
static id aspect_add(id self, SEL selector, AspectOptions options, id block, NSError **error) {
NSCParameterAssert(self);
NSCParameterAssert(selector);
NSCParameterAssert(block);
__block AspectIdentifier *identifier = nil;
//加了个自旋锁，保证整个操作的线程安全
aspect_performLocked(^{
//对传进来的参数进行校验，保证参数合法性
if (aspect_isSelectorAllowedAndTrack(self, selector, options, error)) {
//创建AspectsContainer容器，利用AssociatedObject关联对象，添加到NSObject分类中作为aliasSelector属性
AspectsContainer *aspectContainer = aspect_getContainerForObject(self, selector);
identifier = [AspectIdentifier identifierWithSelector:selector object:self options:options block:block error:error];
if (identifier) {
[aspectContainer addAspect:identifier withOptions:options];
// Modify the class to allow message interception.
aspect_prepareClassAndHookSelector(self, selector, error);
}
}
});
return identifier;
}
//aspect_remove 是整个aspec_add的逆过程
static BOOL aspect_remove(AspectIdentifier *aspect, NSError **error) {
NSCAssert([aspect isKindOfClass:AspectIdentifier.class], @"Must have correct type.");
__block BOOL success = NO;
//保证线程安全
aspect_performLocked(^{
id self = aspect.object; // strongify
if (self) {
AspectsContainer *aspectContainer = aspect_getContainerForObject(self, aspect.selector);
success = [aspectContainer removeAspect:aspect];
//移除之前hook的class 和selector
aspect_cleanupHookedClassAndSelector(self, aspect.selector);
// destroy token
aspect.object = nil;
aspect.block = nil;
aspect.selector = NULL;
}else {
NSString *errrorDesc = [NSString stringWithFormat:@"Unable to deregister hook. Object already deallocated: %@", aspect];
AspectError(AspectErrorRemoveObjectAlreadyDeallocated, errrorDesc);
}
});
return success;
}
static void aspect_performLocked(dispatch_block_t block) {
static OSSpinLock aspect_lock = OS_SPINLOCK_INIT;
//自旋锁，效率较高，OSSpinLock的问题在于，如果访问这个锁的线程不是同一优先级的话，会有死锁的风险。
//这里暂时认为是相同的优先级线程，所以保护了block的线程安全
OSSpinLockLock(&aspect_lock);
block();
OSSpinLockUnlock(&aspect_lock);
}
static SEL aspect_aliasForSelector(SEL selector) {
NSCParameterAssert(selector);
return NSSelectorFromString([AspectsMessagePrefix stringByAppendingFormat:@"_%@", NSStringFromSelector(selector)]);
}
static NSMethodSignature *aspect_blockMethodSignature(id block, NSError **error) {
//因为实现类似，入参block，强制转换成AspectBlockRef类型
AspectBlockRef layout = (__bridge void *)block;
if (!(layout->flags & AspectBlockFlagsHasSignature)) {
//判断是否有AspectBlockFlagsHasSignature，如果没有，则报不包含方法签名的错
NSString *description = [NSString stringWithFormat:@"The block %@ doesn't contain a type signature.", block];
AspectError(AspectErrorMissingBlockSignature, description);
return nil;
}
//block里面对应的descriptor指针
void *desc = layout->descriptor;
//往下偏移两个(unsigned long int)的位置指向了copy函数的地址
/*
对照结构体里面的
unsigned long int reserved;
unsigned long int size;
*/
desc += 2 * sizeof(unsigned long int);
//如果包含Copy 和Dispose 函数
if (layout->flags & AspectBlockFlagsHasCopyDisposeHelpers) {
//继续往下偏移两个(void *)的大小
/*
void (*copy)(void *dst, const void *src);
void (*dispose)(const void *);
*/
desc += 2 * sizeof(void *);
}
//这时指针移动到了const char *signature;
if (!desc) {
//我发现这里和上文的逻辑一样，都是报的AspectErrorMissingBlockSignature。不明白为什么这里的判定条件是if (!desc)，上一段是 layout->flags & AspectBlockFlagsHasCopyDisposeHelpers，为什么上一段不用if (!desc)来判断呢。
NSString *description = [NSString stringWithFormat:@"The block %@ doesn't has a type signature.", block];
AspectError(AspectErrorMissingBlockSignature, description);
return nil;
}
//参考文章中举了一个例子 打印出来一堆type+位移，还是把NSMethodSignature打印出来比较直观
const char *signature = (*(const char **)desc);
return [NSMethodSignature signatureWithObjCTypes:signature];
}
//对比要替换的方法block和原始方法的签名
static BOOL aspect_isCompatibleBlockSignature(NSMethodSignature *blockSignature, id object, SEL selector, NSError **error) {
NSCParameterAssert(blockSignature);
NSCParameterAssert(object);
NSCParameterAssert(selector);
BOOL signaturesMatch = YES;
NSMethodSignature *methodSignature = [[object class] instanceMethodSignatureForSelector:selector];
//这里比较参数个数，两者不一定要相等，block的参数可以比原始参数少。参考文章解读有误
if (blockSignature.numberOfArguments > methodSignature.numberOfArguments) {
signaturesMatch = NO;
}else {
if (blockSignature.numberOfArguments > 1) {
//这里应该是 @"<AspectInfo>"。参考文章解读有误
const char *blockType = [blockSignature getArgumentTypeAtIndex:1];
if (blockType[0] != '@') {
signaturesMatch = NO;
}
}
// Argument 0 is self/block, argument 1 is SEL or id<AspectInfo>. We start comparing at argument 2.
// The block can have less arguments than the method, that's ok.
if (signaturesMatch) {
for (NSUInteger idx = 2; idx < blockSignature.numberOfArguments; idx++) {
const char *methodType = [methodSignature getArgumentTypeAtIndex:idx];
const char *blockType = [blockSignature getArgumentTypeAtIndex:idx];
// Only compare parameter, not the optional type data.
if (!methodType || !blockType || methodType[0] != blockType[0]) {
signaturesMatch = NO; break;
}
}
}
}
if (!signaturesMatch) {
NSString *description = [NSString stringWithFormat:@"Block signature %@ doesn't match %@.", blockSignature, methodSignature];
AspectError(AspectErrorIncompatibleBlockSignature, description);
return NO;
}
return YES;
}
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Class + Selector Preparation
static BOOL aspect_isMsgForwardIMP(IMP impl) {
return impl == _objc_msgForward
#if !defined(__arm64__)
|| impl == (IMP)_objc_msgForward_stret
#endif
;
}
static IMP aspect_getMsgForwardIMP(NSObject *self, SEL selector) {
IMP msgForwardIMP = _objc_msgForward;
#if !defined(__arm64__)
// As an ugly internal runtime implementation detail in the 32bit runtime, we need to determine of the method we hook returns a struct or anything larger than id.
// https://developer.apple.com/library/mac/documentation/DeveloperTools/Conceptual/LowLevelABI/000-Introduction/introduction.html
// https://github.com/ReactiveCocoa/ReactiveCocoa/issues/783
// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042e/IHI0042E_aapcs.pdf (Section 5.4)
Method method = class_getInstanceMethod(self.class, selector);
const char *encoding = method_getTypeEncoding(method);
BOOL methodReturnsStructValue = encoding[0] == _C_STRUCT_B;
if (methodReturnsStructValue) {
@try {
NSUInteger valueSize = 0;
NSGetSizeAndAlignment(encoding, &valueSize, NULL);
if (valueSize == 1 || valueSize == 2 || valueSize == 4 || valueSize == 8) {
methodReturnsStructValue = NO;
}
} @catch (__unused NSException *e) {}
}
if (methodReturnsStructValue) {
msgForwardIMP = (IMP)_objc_msgForward_stret;
}
#endif
return msgForwardIMP;
}
static void aspect_prepareClassAndHookSelector(NSObject *self, SEL selector, NSError **error) {
NSCParameterAssert(selector);
//kclass 是hook完原始的class得到的子类
Class klass = aspect_hookClass(self, error);
Method targetMethod = class_getInstanceMethod(klass, selector);
IMP targetMethodIMP = method_getImplementation(targetMethod);
//判断当前IMP是不是消息转发
if (!aspect_isMsgForwardIMP(targetMethodIMP)) {
// Make a method alias for the existing method implementation, it not already copied.
//如果不是消息转发，获取原始selector对应的IMP的方法编码typeEncoding
const char *typeEncoding = method_getTypeEncoding(targetMethod);
SEL aliasSelector = aspect_aliasForSelector(selector);
if (![klass instancesRespondToSelector:aliasSelector]) {
//如果子类不能响应aspects_xxxx，就为kclass添加aspects_xxxx，
__unused BOOL addedAlias = class_addMethod(klass, aliasSelector, method_getImplementation(targetMethod), typeEncoding);
NSCAssert(addedAlias, @"Original implementation for %@ is already copied to %@ on %@", NSStringFromSelector(selector), NSStringFromSelector(aliasSelector), klass);
}
// We use forwardInvocation to hook in.
//我们将selector 指向_objc_msgForward
class_replaceMethod(klass, selector, aspect_getMsgForwardIMP(self, selector), typeEncoding);
AspectLog(@"Aspects: Installed hook for -[%@ %@].", klass, NSStringFromSelector(selector));
}
}
// Will undo the runtime changes made.
static void aspect_cleanupHookedClassAndSelector(NSObject *self, SEL selector) {
NSCParameterAssert(self);
NSCParameterAssert(selector);
//获取当前self，所指向的isa，
Class klass = object_getClass(self);
BOOL isMetaClass = class_isMetaClass(klass);
if (isMetaClass) {
// 如果是元类，self 为类对象，把klass 指向自己
klass = (Class)self;
}
// Check if the method is marked as forwarded and undo that.
Method targetMethod = class_getInstanceMethod(klass, selector);
IMP targetMethodIMP = method_getImplementation(targetMethod);
if (aspect_isMsgForwardIMP(targetMethodIMP)) {
// Restore the original method implementation.
const char *typeEncoding = method_getTypeEncoding(targetMethod);
SEL aliasSelector = aspect_aliasForSelector(selector);
Method originalMethod = class_getInstanceMethod(klass, aliasSelector);
IMP originalIMP = method_getImplementation(originalMethod);
NSCAssert(originalMethod, @"Original implementation for %@ not found %@ on %@", NSStringFromSelector(selector), NSStringFromSelector(aliasSelector), klass);
class_replaceMethod(klass, selector, originalIMP, typeEncoding);
AspectLog(@"Aspects: Removed hook for -[%@ %@].", klass, NSStringFromSelector(selector));
}
// Deregister global tracked selector
aspect_deregisterTrackedSelector(self, selector);
// Get the aspect container and check if there are any hooks remaining. Clean up if there are not.
AspectsContainer *container = aspect_getContainerForObject(self, selector);
if (!container.hasAspects) {
// Destroy the container
aspect_destroyContainerForObject(self, selector);
// Figure out how the class was modified to undo the changes.
NSString *className = NSStringFromClass(klass);
if ([className hasSuffix:AspectsSubclassSuffix]) {
Class originalClass = NSClassFromString([className stringByReplacingOccurrencesOfString:AspectsSubclassSuffix withString:@""]);
NSCAssert(originalClass != nil, @"Original class must exist");
object_setClass(self, originalClass);
AspectLog(@"Aspects: %@ has been restored.", NSStringFromClass(originalClass));
// We can only dispose the class pair if we can ensure that no instances exist using our subclass.
// Since we don't globally track this, we can't ensure this - but there's also not much overhead in keeping it around.
//objc_disposeClassPair(object.class);
}else {
// Class is most likely swizzled in place. Undo that.
if (isMetaClass) {
aspect_undoSwizzleClassInPlace((Class)self);
}else if (self.class != klass) {
aspect_undoSwizzleClassInPlace(klass);
}
}
}
}
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Hook Class
//hook 完原始的class之后得到的子类，名字都是带有_Aspects_后缀的子类
static Class aspect_hookClass(NSObject *self, NSError **error) {
NSCParameterAssert(self);
/*
+ (Class)class {
return self;
}
获取类对象
*/
Class statedClass = self.class;
/*
Class object_getClass(id obj)
{
if (obj) return obj->getIsa();
else return Nil;
}
获取类的isa
*/
Class baseClass = object_getClass(self);
NSString *className = NSStringFromClass(baseClass);
// Already subclassed 判断类是否已经被hook过
if ([className hasSuffix:AspectsSubclassSuffix]) {
return baseClass;
// We swizzle a class object, not a single object.
}else if (class_isMetaClass(baseClass)) {
//如果baseClass是元类，那么传入的self，是一个类对象
return aspect_swizzleClassInPlace((Class)self);
// Probably a KVO'ed class. Swizzle in place. Also swizzle meta classes in place.
}else if (statedClass != baseClass) {
//如传入的是一个对象，不是类。如果statedClass和baseClass不相等，说明为KVO过的对象。KVO的对象的isa指针会指向一个中间类。对中间类调用aspect_swizzleClassInPlace
return aspect_swizzleClassInPlace(baseClass);
}
// Default case. Create dynamic subclass.
//当className 没有包含@"_Aspects_"后缀，并且也不是元类，不是KVO的中间类，既statedClass == baseClass的情况。于是默认新建一个子类subclass。
/*
设计思想：hook 是在runtime中动态穿件子类的基础上实现的。所有的swizzling 操作都发生在子类，这样做的好处是1.你不需要去更改对象本身的类。当你remove aspects的时候，如果发现当前对象的aspect都被移除了，可以将isa指针重新指回对象本身的类。
2.不会影响到该类的其它对象，可以做到只改变一个对象的行为，不改变该类的其它对象。(看到这里,我觉得作者好聪明啊)
*/
const char *subclassName = [className stringByAppendingString:AspectsSubclassSuffix].UTF8String;
/***********************************************************************
* objc_getClass. Return the id of the named class. If the class does
* not exist, call _objc_classLoader and then objc_classHandler, either of
* which may create a new class.
* Warning: doesn't work if aClassName is the name of a posed-for class's isa!
**********************************************************************/
/*
Class objc_getClass(const char *aClassName)
{
if (!aClassName) return Nil;
// NO unconnected, YES class handler
return look_up_class(aClassName, NO, YES);
}
*/
/***********************************************************************
* look_up_class
* Look up a class by name, and realize it.
* Locking: acquires runtimeLock
**********************************************************************/
/*
Class look_up_class(const char *name,
bool includeUnconnected __attribute__((unused)),
bool includeClassHandler __attribute__((unused)))
{
if (!name) return nil;
Class result;
bool unrealized;
{
//读写锁，底层是用pthread_rwlock_t实现的
rwlock_reader_t lock(runtimeLock);
// 查看有没有实现叫name的class
result = getClass(name);
unrealized = result && !result->isRealized();
}
if (unrealized) {
rwlock_writer_t lock(runtimeLock);
realizeClass(result);
}
return result;
}
*/
Class subclass = objc_getClass(subclassName);
if (subclass == nil) {
//新建这个子类
/***********************************************************************
* objc_allocateClassPair
* fixme
* Locking: acquires runtimeLock
**********************************************************************/
/*
Class objc_allocateClassPair(Class superclass, const char *name,
size_t extraBytes)
{
Class cls, meta;
rwlock_writer_t lock(runtimeLock);
// Fail if the class name is in use.
// Fail if the superclass isn't kosher. //rootOK
if (getClass(name) || !verifySuperclass(superclass, true)) {
return nil;
}
// Allocate new classes.
cls = alloc_class_for_subclass(superclass, extraBytes);
meta = alloc_class_for_subclass(superclass, extraBytes);
// fixme mangle the name if it looks swift-y?
objc_initializeClassPair_internal(superclass, name, cls, meta);
return cls;
}
*/
//baseClass 是入参，superclass
subclass = objc_allocateClassPair(baseClass, subclassName, 0);
if (subclass == nil) {
//新建子类失败，报错
NSString *errrorDesc = [NSString stringWithFormat:@"objc_allocateClassPair failed to allocate class %s.", subclassName];
AspectError(AspectErrorFailedToAllocateClassPair, errrorDesc);
return nil;
}
aspect_swizzleForwardInvocation(subclass);
//subclass isa-> statedClass
aspect_hookedGetClass(subclass, statedClass);
//meta subclass isa-> statedClass
aspect_hookedGetClass(object_getClass(subclass), statedClass);
//注册刚刚新建的subclass
objc_registerClassPair(subclass);
}
//把当前self 的 isa 指向了子类subclass
object_setClass(self, subclass);
//hook 阶段完成，成功把self hook 成了其子类 xxx_Aspects_
return subclass;
}
static NSString *const AspectsForwardInvocationSelectorName = @"__aspects_forwardInvocation:";
static void aspect_swizzleForwardInvocation(Class klass) {
NSCParameterAssert(klass);
// If there is no method, replace will act like class_addMethod.
/***********************************************************************
* class_replaceMethod
**********************************************************************/
/*
IMP class_replaceMethod(Class cls, SEL name, IMP imp, const char *types)
{
if (!cls) return nil;
return _class_addMethod(cls, name, imp, types, YES);
}
static IMP _class_addMethod(Class cls, SEL name, IMP imp,
const char *types, bool replace)
{
old_method *m;
IMP result = nil;
if (!types) types = "";
mutex_locker_t lock(methodListLock);
if ((m = _findMethodInClass(cls, name))) {
// already exists
// fixme atomic
result = method_getImplementation((Method)m);
if (replace) {
method_setImplementation((Method)m, imp);
}
} else {
// fixme could be faster
old_method_list *mlist =
(old_method_list *)calloc(sizeof(old_method_list), 1);
mlist->obsolete = fixed_up_method_list;
mlist->method_count = 1;
mlist->method_list[0].method_name = name;
mlist->method_list[0].method_types = strdup(types);
if (!ignoreSelector(name)) {
mlist->method_list[0].method_imp = imp;
} else {
mlist->method_list[0].method_imp = (IMP)&_objc_ignored_method;
}
_objc_insertMethods(cls, mlist, nil);
if (!(cls->info & CLS_CONSTRUCTING)) {
flush_caches(cls, NO);
} else {
// in-construction class has no subclasses
flush_cache(cls);
}
result = nil;
}
return result;
}
*/
//把forwardInvocation:的IMP替换成__ASPECTS_ARE_BEING_CALLED__,返回的是原方法的IMP
IMP originalImplementation = class_replaceMethod(klass, @selector(forwardInvocation:), (IMP)__ASPECTS_ARE_BEING_CALLED__, "v@:@");
if (originalImplementation) {
//原方法有实现，先添加一个方法__aspects_forwardInvocation，指向原来的实现
class_addMethod(klass, NSSelectorFromString(AspectsForwardInvocationSelectorName), originalImplementation, "v@:@");
}
AspectLog(@"Aspects: %@ is now aspect aware.", NSStringFromClass(klass));
}
static void aspect_undoSwizzleForwardInvocation(Class klass) {
NSCParameterAssert(klass);
Method originalMethod = class_getInstanceMethod(klass, NSSelectorFromString(AspectsForwardInvocationSelectorName));
Method objectMethod = class_getInstanceMethod(NSObject.class, @selector(forwardInvocation:));
// There is no class_removeMethod, so the best we can do is to retore the original implementation, or use a dummy.
IMP originalImplementation = method_getImplementation(originalMethod ?: objectMethod);
class_replaceMethod(klass, @selector(forwardInvocation:), originalImplementation, "v@:@");
AspectLog(@"Aspects: %@ has been restored.", NSStringFromClass(klass));
}
//把class的实例方法替换成statedClass，把调用class时候的isa指向了statedClass
static void aspect_hookedGetClass(Class class, Class statedClass) {
NSCParameterAssert(class);
NSCParameterAssert(statedClass);
Method method = class_getInstanceMethod(class, @selector(class));
IMP newIMP = imp_implementationWithBlock(^(id self) {
return statedClass;
});
class_replaceMethod(class, @selector(class), newIMP, method_getTypeEncoding(method));
}
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Swizzle Class In Place
static void _aspect_modifySwizzledClasses(void (^block)(NSMutableSet *swizzledClasses)) {
static NSMutableSet *swizzledClasses;
static dispatch_once_t pred;
dispatch_once(&pred, ^{
swizzledClasses = [NSMutableSet new];
});
@synchronized(swizzledClasses) {
block(swizzledClasses);
}
}
static Class aspect_swizzleClassInPlace(Class klass) {
NSCParameterAssert(klass);
NSString *className = NSStringFromClass(klass);
_aspect_modifySwizzledClasses(^(NSMutableSet *swizzledClasses) {
if (![swizzledClasses containsObject:className]) {
aspect_swizzleForwardInvocation(klass);
[swizzledClasses addObject:className];
}
});
return klass;
}
static void aspect_undoSwizzleClassInPlace(Class klass) {
NSCParameterAssert(klass);
NSString *className = NSStringFromClass(klass);
_aspect_modifySwizzledClasses(^(NSMutableSet *swizzledClasses) {
if ([swizzledClasses containsObject:className]) {
aspect_undoSwizzleForwardInvocation(klass);
[swizzledClasses removeObject:className];
}
});
}
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Aspect Invoke Point
// This is a macro so we get a cleaner stack trace.
#define aspect_invoke(aspects, info) \
for (AspectIdentifier *aspect in aspects) {\
[aspect invokeWithInfo:info];\
if (aspect.options & AspectOptionAutomaticRemoval) { \
aspectsToRemove = [aspectsToRemove?:@[] arrayByAddingObject:aspect]; \
} \
}
// This is the swizzled forwardInvocation: method.核心实现
static void __ASPECTS_ARE_BEING_CALLED__(__unsafe_unretained NSObject *self, SEL selector, NSInvocation *invocation) {
NSCParameterAssert(self);
NSCParameterAssert(invocation);
//获取原始selector
SEL originalSelector = invocation.selector;
//获取带有aspects_xxx前缀的方法
SEL aliasSelector = aspect_aliasForSelector(invocation.selector);
//替换selector
invocation.selector = aliasSelector;
//获得实例对象的容器
AspectsContainer *objectContainer = objc_getAssociatedObject(self, aliasSelector);
//获取类对象的容器
AspectsContainer *classContainer = aspect_getContainerForClass(object_getClass(self), aliasSelector);
//初始化 AspectInfo
AspectInfo *info = [[AspectInfo alloc] initWithInstance:self invocation:invocation];
//存放需要被remove的Aspects
NSArray *aspectsToRemove = nil;
// Before hooks.
//执行对应的传入block
aspect_invoke(classContainer.beforeAspects, info);
aspect_invoke(objectContainer.beforeAspects, info);
// Instead hooks.
BOOL respondsToAlias = YES;
//判断当前insteadAspects是否有数据
if (objectContainer.insteadAspects.count || classContainer.insteadAspects.count) {
aspect_invoke(classContainer.insteadAspects, info);
aspect_invoke(objectContainer.insteadAspects, info);
}else {
//如果没有数据
Class klass = object_getClass(invocation.target);
do {//判断当前继承链是否能响应aspects_xxx,这里aliasSelector是原方法
if ((respondsToAlias = [klass instancesRespondToSelector:aliasSelector])) {
[invocation invoke];
break;
}
}while (!respondsToAlias && (klass = class_getSuperclass(klass)));
}
// After hooks.
aspect_invoke(classContainer.afterAspects, info);
aspect_invoke(objectContainer.afterAspects, info);
// If no hooks are installed, call original implementation (usually to throw an exception)
//如果hook没有被正常执行，执行原来的方法
if (!respondsToAlias) {
invocation.selector = originalSelector;
SEL originalForwardInvocationSEL = NSSelectorFromString(AspectsForwardInvocationSelectorName);
if ([self respondsToSelector:originalForwardInvocationSEL]) {
((void( *)(id, SEL, NSInvocation *))objc_msgSend)(self, originalForwardInvocationSEL, invocation);
}else {
//移除方法
[self doesNotRecognizeSelector:invocation.selector];
}
}
// Remove any hooks that are queued for deregistration.
[aspectsToRemove makeObjectsPerformSelector:@selector(remove)];
}
#undef aspect_invoke
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Aspect Container Management
// Loads or creates the aspect container.
static AspectsContainer *aspect_getContainerForObject(NSObject *self, SEL selector) {
NSCParameterAssert(self);
SEL aliasSelector = aspect_aliasForSelector(selector);
AspectsContainer *aspectContainer = objc_getAssociatedObject(self, aliasSelector);
if (!aspectContainer) {
aspectContainer = [AspectsContainer new];
objc_setAssociatedObject(self, aliasSelector, aspectContainer, OBJC_ASSOCIATION_RETAIN);
}
return aspectContainer;
}
static AspectsContainer *aspect_getContainerForClass(Class klass, SEL selector) {
NSCParameterAssert(klass);
AspectsContainer *classContainer = nil;
do {
classContainer = objc_getAssociatedObject(klass, selector);
if (classContainer.hasAspects) break;
}while ((klass = class_getSuperclass(klass)));
return classContainer;
}
static void aspect_destroyContainerForObject(id<NSObject> self, SEL selector) {
NSCParameterAssert(self);
SEL aliasSelector = aspect_aliasForSelector(selector);
objc_setAssociatedObject(self, aliasSelector, nil, OBJC_ASSOCIATION_RETAIN);
}
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - Selector Blacklist Checking
static NSMutableDictionary *aspect_getSwizzledClassesDict() {
static NSMutableDictionary *swizzledClassesDict;
static dispatch_once_t pred;
dispatch_once(&pred, ^{
swizzledClassesDict = [NSMutableDictionary new];
});
return swizzledClassesDict;
}
static BOOL aspect_isSelectorAllowedAndTrack(NSObject *self, SEL selector, AspectOptions options, NSError **error) {
static NSSet *disallowedSelectorList;
static dispatch_once_t pred;
dispatch_once(&pred, ^{
disallowedSelectorList = [NSSet setWithObjects:@"retain", @"release", @"autorelease", @"forwardInvocation:", nil];
});
// Check against the blacklist.
NSString *selectorName = NSStringFromSelector(selector);
//黑名单不行
if ([disallowedSelectorList containsObject:selectorName]) {
NSString *errorDescription = [NSString stringWithFormat:@"Selector %@ is blacklisted.", selectorName];
AspectError(AspectErrorSelectorBlacklisted, errorDescription);
return NO;
}
// Additional checks.
AspectOptions position = options&AspectPositionFilter;
if ([selectorName isEqualToString:@"dealloc"] && position != AspectPositionBefore) {
//描述的很清楚
NSString *errorDesc = @"AspectPositionBefore is the only valid position when hooking dealloc.";
AspectError(AspectErrorSelectorDeallocPosition, errorDesc);
return NO;
}
if (![self respondsToSelector:selector] && ![self.class instancesRespondToSelector:selector]) {
//这里也描述的很清楚
NSString *errorDesc = [NSString stringWithFormat:@"Unable to find selector -[%@ %@].", NSStringFromClass(self.class), selectorName];
AspectError(AspectErrorDoesNotRespondToSelector, errorDesc);
return NO;
}
// Search for the current class and the class hierarchy IF we are modifying a class object
//先判断是不是元类
if (class_isMetaClass(object_getClass(self))) {
Class klass = [self class];
//一个static 的字典，key 为Class， value 为 AspectTracker
NSMutableDictionary *swizzledClassesDict = aspect_getSwizzledClassesDict();
Class currentClass = [self class];
AspectTracker *tracker = swizzledClassesDict[currentClass];
//第一块判断逻辑，tracker 的 subclassHasHookedSelectorName 方法判断
if ([tracker subclassHasHookedSelectorName:selectorName]) {
NSSet *subclassTracker = [tracker subclassTrackersHookingSelectorName:selectorName];
NSSet *subclassNames = [subclassTracker valueForKey:@"trackedClassName"];
NSString *errorDescription = [NSString stringWithFormat:@"Error: %@ already hooked subclasses: %@. A method can only be hooked once per class hierarchy.", selectorName, subclassNames];
AspectError(AspectErrorSelectorAlreadyHookedInClassHierarchy, errorDescription);
return NO;
}
//第二块判断逻辑，一直往上找
do {
tracker = swizzledClassesDict[currentClass];
if ([tracker.selectorNames containsObject:selectorName]) {
//这个逻辑不太确认，不知道为啥能判断是topmost
if (klass == currentClass) {
// Already modified and topmost!
return YES;
}
NSString *errorDescription = [NSString stringWithFormat:@"Error: %@ already hooked in %@. A method can only be hooked once per class hierarchy.", selectorName, NSStringFromClass(currentClass)];
AspectError(AspectErrorSelectorAlreadyHookedInClassHierarchy, errorDescription);
return NO;
}
//从currentClass 的super class ，会一直执向NSObject(meta)->NSObject->nil
} while ((currentClass = class_getSuperclass(currentClass)));
// Add the selector as being modified.
currentClass = klass;
AspectTracker *subclassTracker = nil;
//第三块构造逻辑，我咋觉得这个逻辑不应该写在这里，这端和判断其实没关系了，只是为了从下往上构造subclassTracker 链
do {
tracker = swizzledClassesDict[currentClass];
if (!tracker) {
tracker = [[AspectTracker alloc] initWithTrackedClass:currentClass];
swizzledClassesDict[(id<NSCopying>)currentClass] = tracker;
}
if (subclassTracker) {
[tracker addSubclassTracker:subclassTracker hookingSelectorName:selectorName];
} else {
[tracker.selectorNames addObject:selectorName];
}
// All superclasses get marked as having a subclass that is modified.
subclassTracker = tracker;
}while ((currentClass = class_getSuperclass(currentClass)));
} else {
return YES;
}
return YES;
}
static void aspect_deregisterTrackedSelector(id self, SEL selector) {
if (!class_isMetaClass(object_getClass(self))) return;
NSMutableDictionary *swizzledClassesDict = aspect_getSwizzledClassesDict();
NSString *selectorName = NSStringFromSelector(selector);
Class currentClass = [self class];
AspectTracker *subclassTracker = nil;
do {
AspectTracker *tracker = swizzledClassesDict[currentClass];
if (subclassTracker) {
[tracker removeSubclassTracker:subclassTracker hookingSelectorName:selectorName];
} else {
[tracker.selectorNames removeObject:selectorName];
}
if (tracker.selectorNames.count == 0 && tracker.selectorNamesToSubclassTrackers) {
[swizzledClassesDict removeObjectForKey:currentClass];
}
subclassTracker = tracker;
}while ((currentClass = class_getSuperclass(currentClass)));
}
@end
@implementation AspectTracker
- (id)initWithTrackedClass:(Class)trackedClass {
if (self = [super init]) {
_trackedClass = trackedClass;
_selectorNames = [NSMutableSet new];
_selectorNamesToSubclassTrackers = [NSMutableDictionary new];
}
return self;
}
- (BOOL)subclassHasHookedSelectorName:(NSString *)selectorName {
return self.selectorNamesToSubclassTrackers[selectorName] != nil;
}
- (void)addSubclassTracker:(AspectTracker *)subclassTracker hookingSelectorName:(NSString *)selectorName {
NSMutableSet *trackerSet = self.selectorNamesToSubclassTrackers[selectorName];
if (!trackerSet) {
trackerSet = [NSMutableSet new];
self.selectorNamesToSubclassTrackers[selectorName] = trackerSet;
}
[trackerSet addObject:subclassTracker];
}
- (void)removeSubclassTracker:(AspectTracker *)subclassTracker hookingSelectorName:(NSString *)selectorName {
NSMutableSet *trackerSet = self.selectorNamesToSubclassTrackers[selectorName];
[trackerSet removeObject:subclassTracker];
//如果这个selectorName对应的set空了，则删除这一键值对
if (trackerSet.count == 0) {
[self.selectorNamesToSubclassTrackers removeObjectForKey:selectorName];
}
}
- (NSSet *)subclassTrackersHookingSelectorName:(NSString *)selectorName {
NSMutableSet *hookingSubclassTrackers = [NSMutableSet new];
for (AspectTracker *tracker in self.selectorNamesToSubclassTrackers[selectorName]) {
if ([tracker.selectorNames containsObject:selectorName]) {
[hookingSubclassTrackers addObject:tracker];
}
[hookingSubclassTrackers unionSet:[tracker subclassTrackersHookingSelectorName:selectorName]];
}
return hookingSubclassTrackers;
}
- (NSString *)trackedClassName {
return NSStringFromClass(self.trackedClass);
}
- (NSString *)description {
return [NSString stringWithFormat:@"<%@: %@, trackedClass: %@, selectorNames:%@, subclass selector names: %@>", self.class, self, NSStringFromClass(self.trackedClass), self.selectorNames, self.selectorNamesToSubclassTrackers.allKeys];
}
@end
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - NSInvocation (Aspects)
@implementation NSInvocation (Aspects)
// Thanks to the ReactiveCocoa team for providing a generic solution for this.
- (id)aspect_argumentAtIndex:(NSUInteger)index {
//用来获取mthoedSignature 方法签名指定index的type encoding字符串
const char *argType = [self.methodSignature getArgumentTypeAtIndex:index];
// Skip const type qualifier.
//_C_CONST是一个常量，用来判断encoding的字符串是不是CONST常量
//#define _C_CONST 'r'
if (argType[0] == _C_CONST) argType++;
// 这个宏定义的目的是，把基本数据类型，给包装成一个对象
#define WRAP_AND_RETURN(type) do { type val = 0; [self getArgument:&val atIndex:(NSInteger)index]; return @(val); } while (0)
//判断了 id Class，注意这里用了__autoreleasing 修饰
if (strcmp(argType, @encode(id)) == 0 || strcmp(argType, @encode(Class)) == 0) {
__autoreleasing id returnObj;
[self getArgument:&returnObj atIndex:(NSInteger)index];
return returnObj;
} else if (strcmp(argType, @encode(SEL)) == 0) {
//判断了SEL
SEL selector = 0;
[self getArgument:&selector atIndex:(NSInteger)index];
return NSStringFromSelector(selector);
} else if (strcmp(argType, @encode(Class)) == 0) {
//这里怎么和上面一样，是写错了吗？？？
__autoreleasing Class theClass = Nil;
[self getArgument:&theClass atIndex:(NSInteger)index];
return theClass;
// Using this list will box the number with the appropriate constructor, instead of the generic NSValue.
} else if (strcmp(argType, @encode(char)) == 0) {
WRAP_AND_RETURN(char);
} else if (strcmp(argType, @encode(int)) == 0) {
WRAP_AND_RETURN(int);
} else if (strcmp(argType, @encode(short)) == 0) {
WRAP_AND_RETURN(short);
} else if (strcmp(argType, @encode(long)) == 0) {
WRAP_AND_RETURN(long);
} else if (strcmp(argType, @encode(long long)) == 0) {
WRAP_AND_RETURN(long long);
} else if (strcmp(argType, @encode(unsigned char)) == 0) {
WRAP_AND_RETURN(unsigned char);
} else if (strcmp(argType, @encode(unsigned int)) == 0) {
WRAP_AND_RETURN(unsigned int);
} else if (strcmp(argType, @encode(unsigned short)) == 0) {
WRAP_AND_RETURN(unsigned short);
} else if (strcmp(argType, @encode(unsigned long)) == 0) {
WRAP_AND_RETURN(unsigned long);
} else if (strcmp(argType, @encode(unsigned long long)) == 0) {
WRAP_AND_RETURN(unsigned long long);
} else if (strcmp(argType, @encode(float)) == 0) {
WRAP_AND_RETURN(float);
} else if (strcmp(argType, @encode(double)) == 0) {
WRAP_AND_RETURN(double);
} else if (strcmp(argType, @encode(BOOL)) == 0) {
WRAP_AND_RETURN(BOOL);
} else if (strcmp(argType, @encode(bool)) == 0) {
WRAP_AND_RETURN(BOOL);
} else if (strcmp(argType, @encode(char *)) == 0) {
WRAP_AND_RETURN(const char *);
} else if (strcmp(argType, @encode(void (^)(void))) == 0) {
//判断block，注意这里用了__unsafe_unretained
__unsafe_unretained id block = nil;
[self getArgument:&block atIndex:(NSInteger)index];
return [block copy];
} else {
//判断struct 结构体，返回NSValue对象
NSUInteger valueSize = 0;
NSGetSizeAndAlignment(argType, &valueSize, NULL);
unsigned char valueBytes[valueSize];
[self getArgument:valueBytes atIndex:(NSInteger)index];
return [NSValue valueWithBytes:valueBytes objCType:argType];
}
return nil;//这句话，让代码更健壮
#undef WRAP_AND_RETURN //及时undef，是一个好习惯
}
- (NSArray *)aspects_arguments {
NSMutableArray *argumentsArray = [NSMutableArray array];
//为啥从2开始？参考https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html
//通过methodSignature打印出来的结果，比numberOfArguments 应该是多一位的
//返回值type，这一位不能算进去
//0 隐藏参数self的type【@ An object (whether statically typed or typed id)】
//1 隐藏参数type【:A method selector (SEL)】
//2 第3位开始，是入参。
for (NSUInteger idx = 2; idx < self.methodSignature.numberOfArguments; idx++) {
[argumentsArray addObject:[self aspect_argumentAtIndex:idx] ?: NSNull.null];
}
return [argumentsArray copy];
}
@end
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - AspectIdentifier
@implementation AspectIdentifier
//逻辑都在两个静态方法内，做block签名类型转换，做签名兼容性校验
+ (instancetype)identifierWithSelector:(SEL)selector object:(id)object options:(AspectOptions)options block:(id)block error:(NSError **)error {
NSCParameterAssert(block);
NSCParameterAssert(selector);
NSMethodSignature *blockSignature = aspect_blockMethodSignature(block, error); // TODO: check signature compatibility, etc.
if (!aspect_isCompatibleBlockSignature(blockSignature, object, selector, error)) {
return nil;
}
AspectIdentifier *identifier = nil;
if (blockSignature) {
identifier = [AspectIdentifier new];
identifier.selector = selector;
identifier.block = block;
identifier.blockSignature = blockSignature;
identifier.options = options;
identifier.object = object; // weak 不会ratain 外部对象
}
return identifier;
}
//执行block方法
- (BOOL)invokeWithInfo:(id<AspectInfo>)info {
NSInvocation *blockInvocation = [NSInvocation invocationWithMethodSignature:self.blockSignature];
NSInvocation *originalInvocation = info.originalInvocation;
NSUInteger numberOfArguments = self.blockSignature.numberOfArguments;
// Be extra paranoid. We already check that on hook registration.
//其实在方法aspect_isCompatibleBlockSignature内部已经做过参数个数的校验了
if (numberOfArguments > originalInvocation.methodSignature.numberOfArguments) {
AspectLogError(@"Block has too many arguments. Not calling %@", info);
return NO;
}
// The `self` of the block will be the AspectInfo. Optional.
if (numberOfArguments > 1) {
//把AspectInfo 存入blockInvocation中
[blockInvocation setArgument:&info atIndex:1];
}
void *argBuf = NULL;
for (NSUInteger idx = 2; idx < numberOfArguments; idx++) {
const char *type = [originalInvocation.methodSignature getArgumentTypeAtIndex:idx];
NSUInteger argSize;
NSGetSizeAndAlignment(type, &argSize, NULL);
if (!(argBuf = reallocf(argBuf, argSize))) {
AspectLogError(@"Failed to allocate memory for block invocation.");
return NO;
}
[originalInvocation getArgument:argBuf atIndex:idx];
[blockInvocation setArgument:argBuf atIndex:idx];
}
[blockInvocation invokeWithTarget:self.block];
if (argBuf != NULL) {
free(argBuf);
}
return YES;
}
- (NSString *)description {
return [NSString stringWithFormat:@"<%@: %p, SEL:%@ object:%@ options:%tu block:%@ (#%tu args)>", self.class, self, NSStringFromSelector(self.selector), self.object, self.options, self.block, self.blockSignature.numberOfArguments];
}
- (BOOL)remove {
return aspect_remove(self, NULL);
}
@end
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - AspectsContainer
@implementation AspectsContainer
- (BOOL)hasAspects {
return self.beforeAspects.count > 0 || self.insteadAspects.count > 0 || self.afterAspects.count > 0;
}
- (void)addAspect:(AspectIdentifier *)aspect withOptions:(AspectOptions)options {
NSParameterAssert(aspect);
/*
分别是 0
1
10
100
& ---------
111（7）AspectPositionFilter
----------
能传入多个组合值吗？为啥这里要做与运算
*/
NSUInteger position = options&AspectPositionFilter;
switch (position) {
case AspectPositionBefore: self.beforeAspects = [(self.beforeAspects ?:@[]) arrayByAddingObject:aspect]; break;
case AspectPositionInstead: self.insteadAspects = [(self.insteadAspects?:@[]) arrayByAddingObject:aspect]; break;
case AspectPositionAfter: self.afterAspects = [(self.afterAspects ?:@[]) arrayByAddingObject:aspect]; break;
}
}
- (BOOL)removeAspect:(id)aspect {
for (NSString *aspectArrayName in @[NSStringFromSelector(@selector(beforeAspects)),
NSStringFromSelector(@selector(insteadAspects)),
NSStringFromSelector(@selector(afterAspects))]) {
NSArray *array = [self valueForKey:aspectArrayName];
NSUInteger index = [array indexOfObjectIdenticalTo:aspect];
if (array && index != NSNotFound) {
NSMutableArray *newArray = [NSMutableArray arrayWithArray:array];
[newArray removeObjectAtIndex:index];
[self setValue:newArray forKey:aspectArrayName];
return YES;
}
}
return NO;
}
- (NSString *)description {
return [NSString stringWithFormat:@"<%@: %p, before:%@, instead:%@, after:%@>", self.class, self, self.beforeAspects, self.insteadAspects, self.afterAspects];
}
@end
///////////////////////////////////////////////////////////////////////////////////////////
#pragma mark - AspectInfo
@implementation AspectInfo
@synthesize arguments = _arguments;
- (id)initWithInstance:(__unsafe_unretained id)instance invocation:(NSInvocation *)invocation {
NSCParameterAssert(instance);
NSCParameterAssert(invocation);
if (self = [super init]) {
_instance = instance;//把外面传进来的实例instance
_originalInvocation = invocation;//原始的invocation保存到对应的成员变量
}
return self;
}
//懒加载，返回原始invocation的aspects_arguments数组，作者为NSInvocation添加了一个分类
- (NSArray *)arguments {
// Lazily evaluate arguments, boxing is expensive.
if (!_arguments) {
_arguments = self.originalInvocation.aspects_arguments;
}
return _arguments;
}
@end
