OC Runtime(二)：Messaging Part II：手动实现objc_sendMsg

1
2
3
4
5
6
typedef objc_method *Method
struct objc_method {
  SEL method_name       OBJC2_UNAVAILABLE; //method 的 selector，SEL
  char *method_types    OBJC2_UNAVAILABLE; //method 的 输入输出参数类型, signature
  IMP method_imp        OBJC2_UNAVAILABLE; //method 的 实现，IMP
} 

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Swizzle.h

# import <Foundation/Foundation.h>
# import <objc/runtime.h>
@interface Swizzle : NSObject
+(void)swizzleClass:(id)objecClass fromSelector:(SEL)sel1 toSelector:(SEL)sel2;
@end


Swizzle.m

@implementation Swizzle


+(void)swizzleClass:(id)objecClass fromSelector:(SEL)sel1 toSelector:(SEL)sel2{
  
  Method originalMethod = class_getInstanceMethod(objecClass, sel1);
  Method destinationMethod = class_getInstanceMethod(objecClass, sel2);
  
  IMP originIMP = method_getImplementation(originalMethod);
  IMP destinationIMP = method_getImplementation(destinationMethod);
  
  BOOL isAdded = class_addMethod(objecClass, sel1, destinationIMP, method_getTypeEncoding(destinationMethod));
  
  if(isAdded){
    class_replaceMethod(objecClass, sel2, originIMP, method_getTypeEncoding(originalMethod));
  }else{
    method_exchangeImplementations(originalMethod, destinationMethod);
  }
}
@end

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
NSString *originalString = @"hello,WORLD!";
NSLog(@"original string  : %@",originalString);
NSLog(@"before Method Swizzle---------");
NSLog(@"lower case String: %@", [originalString lowercaseString]);
NSLog(@"upper case string: %@", [originalString uppercaseString]);
NSLog(@"after  Method Swizzle---------");
[Swizzle swizzleClass:[originalString class]
       fromSelector:@selector(lowercaseString)
         toSelector:@selector(uppercaseString)];
NSLog(@"lower case String: %@", [originalString lowercaseString]);
NSLog(@"upper case string: %@", [originalString uppercaseString]);

//输出：
//original string  : hello,WORLD!
//before Method Swizzle---------
//lower case String: hello,world!
//upper case string: HELLO,WORLD!
//after  Method Swizzle---------
//lower case String: HELLO,WORLD!
//upper case string: hello,world!

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
UIViewController + Swizzle.h

# import <UIKit/UIKit.h>
# import "Swizzle.h"

@interface UIViewController (Swizzle)
-(void)swizzle_viewDidAppear:(BOOL)animated;
@end


UIViewController + Swizzle.m

@implementation UIViewController (Swizzle)

+(void)load{
  [Swizzle swizzleClass:[self class] fromSelector:@selector(viewDidAppear:) toSelector:@selector(swizzle_viewDidAppear:)];
}

-(void)swizzle_viewDidAppear:(BOOL)animated{
  [self swizzle_viewDidAppear:animated];
  NSLog(@"the current appeared ViewController: %@",[self class]);
}


@end

1
2
3
4
5
6
7
8
//输出：
//the current appeared ViewController: UITabBarController
//the current appeared ViewController: UINavigationController
//the current appeared ViewController: PBBibleBookViewController
//the current appeared ViewController: UIInputWindowController
//the current appeared ViewController: PBBibleVolumeViewController
//the current appeared ViewController: PBBibleChapterViewController
//

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
@implementation ConcreteSubjectA

-(NSMutableArray *)Observers{
    if(!_Observers){
        _Observers = [NSMutableArray array];
    }
    return _Observers;
}

-(void)LAL_addObserver:(id<LAL_Observer>)observer WithBlock:(LALObservingBlock)block{
    [observer setObservingBlock:block];
    [self.Observers addObject:observer];

}

-(void)LAL_notify{
    for (id<LAL_Observer> observer in self.Observers) {
        [observer LAL_update];
    }
}

-(void)LAL_removeObserver:(id<LAL_Observer>)observer{
    [self.Observers removeObject:observer];
}

-(void)setAge:(NSNumber *)age{
    _age = age;
    [self LAL_notify];//iVar age 改变后通知Observers.
}
@end

1
2
3
4
5
6
7
8
9
10
#import <Foundation/Foundation.h>
typedef void (^LALKVOBlock)(id obsever, id subject, NSString *keyPath, id oldValue, id newValue);

@interface NSObject (LALKVO)

-(void)LALKVO_addObserver:(id)observer ForKeyPath:(NSString *)keyPath withBlock:(LALKVOBlock)block;

-(void)LALKVO_removeObserver:(id)observer ForKeyPath:(NSString *)keyPath;

@end

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
-(void)LALKVO_addObserver:(id)observer ForKeyPath:(NSString *)keyPath withBlock:(__autoreleasing LALKVOBlock)block{
    //assume the original class is Person
    Class originalClass = [self class];
    
    //step1: keyPath is valid or not.
    SEL keyPathSetter = NSSelectorFromString(setterForGetter(keyPath));
    Method keyPathSetterMethod = class_getInstanceMethod(originalClass, keyPathSetter);
    if(!keyPathSetterMethod){
        NSLog(@"the keyPath is not valid!");
        return;
    }
    
    //step2: intermediate Class exist or not, if not create it LALKVO_Person as the intermediate Class.
    const char *originalClassName = class_getName(originalClass);
    const char *intermediateClassName = getIntermediateClassName(originalClassName);
    if(!objc_getClass(intermediateClassName)){
        createIntermediateClass(self, originalClassName, intermediateClassName);
    }
    
    //step3: override the setter in LALKVO_Person.
        //LALKVO_Person 是否有setter
    Class intermediateClass = object_getClass(self);

    if(!hasSelector(self, keyPathSetter)){
        //没有则创建.
        Method originalKeyPathSetterMethod = class_getInstanceMethod(originalClass, keyPathSetter);
        const char* types = method_getTypeEncoding(originalKeyPathSetterMethod);
        class_addMethod(intermediateClass, keyPathSetter, (IMP)kvo_setter, types);
    }
    //setp4: add the observer to the subject.
    NSMutableArray *observeInfoArray = objc_getAssociatedObject(self, kLALKVOObserverInfoArray);
    if(!observeInfoArray){
        observeInfoArray = [[NSMutableArray alloc] init];
        objc_setAssociatedObject(self, kLALKVOObserverInfoArray, observeInfoArray, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    ObserveInfo *observeInfo = [[ObserveInfo alloc] initWithSubject:self keyPath:keyPath observer:observer block:block];
    if(!observeInfoArrayContainsObserveInfo(observeInfoArray, observeInfo)){
        [observeInfoArray addObject:observeInfo];
    }
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
void kvo_setter(id obj, SEL _cmd, id newValue){
    
    NSString *setterName = NSStringFromSelector(_cmd);
    NSString *getterName = getterForSetter(setterName);
    
    //get the originalClass getter IMP and implement it.
    Method getterMethodFromOriginalClass = class_getInstanceMethod(class_getSuperclass(object_getClass(obj)), NSSelectorFromString(getterName));
    IMP getterIMPFromOriginalClass = method_getImplementation(getterMethodFromOriginalClass);
    id (*getterIMPFromOriginalClassCasted)(id,SEL) = (void *)getterIMPFromOriginalClass;
    id oldValue = getterIMPFromOriginalClassCasted(obj,NSSelectorFromString(getterName));
    
    
    //get the originalClass setter IMP, and implement it.
    Method setterMethodFromOriginalClass = class_getInstanceMethod(class_getSuperclass(object_getClass(obj)), _cmd);
    IMP setterIMPFromOriginalClass = method_getImplementation(setterMethodFromOriginalClass);
    void (*setterIMPFromOriginalClassCasted)(id, SEL, id) = (void *)setterIMPFromOriginalClass;
    setterIMPFromOriginalClassCasted(obj, _cmd, newValue);
    
    //call the block for each observer.
    NSMutableArray *observerInfoArray = objc_getAssociatedObject(obj, kLALKVOObserverInfoArray);
    for (ObserveInfo *observeInfo in observerInfoArray){
        if([observeInfo.keyPath isEqualToString:getterName]){
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                observeInfo.block(observeInfo.observer, observeInfo.subject, observeInfo.keyPath, oldValue, newValue);
            });
        }
    }
}

1
2
3
4
5
6
7
8
9
10
11
12
13
#import <Foundation/Foundation.h>
typedef void (^LALKVOBlock)(id obsever, id subject, NSString *keyPath, id oldValue, id newValue);
static NSNumber *LALKVO_overrideKeyPathSetterFlag;
static void (*originalSetterIMP)(id, SEL,id);

@interface NSObject (LALKVO)

-(void)LALKVO_addObserver:(id)observer ForKeyPath:(NSString *)keyPath withBlock:(LALKVOBlock)block;
-(void)LALKVO_removeObserver:(id)observer ForKeyPath:(NSString *)keyPath;

+(NSNumber *)overrideFlag;
+(void)setOverrideFlag:(NSNumber *)flag;
@end

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
-(void)LALKVO_addObserver:(id)observer ForKeyPath:(NSString *)keyPath withBlock:(__autoreleasing LALKVOBlock)block{
    
    Class originalClass = object_getClass(self);
    //step1: keyPath is valid or not
    SEL keyPathSetter = NSSelectorFromString(setterForGetter(keyPath));
    Method keyPathSetterMethod = class_getInstanceMethod(originalClass, keyPathSetter);
    if(!keyPathSetterMethod){
        NSLog(@"the keyPath is not valid!");
        return;
    }
    //step2: override the setter class, 查看overrideFlag
        //self 是否已经改写setter
    if(![[object_getClass(self) overrideFlag] boolValue]){
        //获取original Setter Method and IMP
        Method originalKeyPathSetterMethod = class_getInstanceMethod(originalClass, keyPathSetter);
        originalSetterIMP =(void *) method_getImplementation(originalKeyPathSetterMethod);

        method_setImplementation(originalKeyPathSetterMethod, (IMP)kvo_setter);
    }
    
    // setp3: add the observer to the subject.
    NSMutableArray *observeInfoArray = objc_getAssociatedObject(self, kLALKVOObserverInfoArray);
    if(!observeInfoArray){
        observeInfoArray = [[NSMutableArray alloc] init];
        objc_setAssociatedObject(self, kLALKVOObserverInfoArray, observeInfoArray, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    ObserveInfo *observeInfo = [[ObserveInfo alloc] initWithSubject:self keyPath:keyPath observer:observer block:block];
    if(!observeInfoArrayContainsObserveInfo(observeInfoArray, observeInfo)){
        [observeInfoArray addObject:observeInfo];
    }
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
void kvo_setter(id obj, SEL _cmd, id newValue){
    
    NSString *setterName = NSStringFromSelector(_cmd);
    NSString *getterName = getterForSetter(setterName);
    
    //get the class getter IMP, and implement it.
    Method getterMethodFromOriginalClass = class_getInstanceMethod(object_getClass(obj), NSSelectorFromString(getterName));
    IMP getterIMPFromOriginalClass = method_getImplementation(getterMethodFromOriginalClass);
    id (*getterIMPFromOriginalClassCasted)(id,SEL) = (void *)getterIMPFromOriginalClass;
    id oldValue = getterIMPFromOriginalClassCasted(obj,NSSelectorFromString(getterName));
    
    //get the class setter IMP, and implement it.
    originalSetterIMP(obj, _cmd, newValue);
    
    NSMutableArray *observerInfoArray = objc_getAssociatedObject(obj, kLALKVOObserverInfoArray);
    for (ObserveInfo *observeInfo in observerInfoArray){
        if([observeInfo.keyPath isEqualToString:getterName]){
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                observeInfo.block(observeInfo.observer, observeInfo.subject, observeInfo.keyPath, oldValue, newValue);
            });
        }
    }
    LALKVO_overrideKeyPathSetterFlag = [NSNumber numberWithBool:YES];
}