消息发送

objc_msgSend流程

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动态方法解析流程

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- (void)test1{}
+ (void)test2{}
void c_test(id self, SEL _cmd){}
// - 对象方法的动态解析
+ (BOOL)resolveClassMethod:(SEL)sel{
    if (sel == @selector(test)) {
        // - 添加test方法, 并将test的方法实现改为test2的方法实现
        Method method = class_getInstanceMethod(self, @selector(test1));
        class_addMethod(self, sel, method_getImplementation(method), method_getTypeEncoding(method));
        return YES;
        
        // - 2. 添加C语言函数, 并将test的方法实现改为c_test的函数实现
        class_addMethod(self, sel, (IMP)c_test, "v16@0:8");

    }
    return [super resolveClassMethod:sel];
}

// - 实例方法的动态解析
+ (BOOL)resolveInstanceMethod:(SEL)sel{
    // - 1. 添加test方法, 并将test的方法实现改为test2的方法实现
    if (sel == @selector(test)) {
        Method method = class_getClassMethod(object_getClass(self), @selector(test2));
        class_addMethod(object_getClass(self), sel, method_getImplementation(method), method_getTypeEncoding(method));
        return YES;
        
        // - 2. 添加C语言函数, 并将test的方法实现改为c_test的函数实现
        class_addMethod(self, sel, (IMP)c_test, "v16@0:8");
    }
    return  [super resolveInstanceMethod:sel];
}

消息转发流程

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-(void)test{}
-(void)test1{}
+(void)test2{}
+(int)test:(int)age height:(float)height{ }
// - 快转发, 让cat去调用test方法
- (id)forwardingTargetForSelector:(SEL)aSelector{
    if (aSelector == @selector(test)) {
        // - 实例方法
        return  [Cat new];
        
        // - 类方法
        return [Cat class]
    }
    return [super forwardingTargetForSelector:aSelector];
}

// - 慢转发, 让cat去调用test方法
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{
    if (aSelector == @selector(test)) {
        // - 没有参数的签名
        return [NSMethodSignature signatureWithObjCTypes:"v16@0:8"];
    }
    
    if (aSelector == @selector(test:height:)) {
        // - 有参数的签名
        return [NSMethodSignature signatureWithObjCTypes:"i24@0:8i16f20"];
    }

    return [super methodSignatureForSelector:aSelector];
}

- (void)forwardInvocation:(NSInvocation *)anInvocation{
    // - 让cat去调用方法
    [anInvocation invokeWithTarget:[Cat new]];

    // - 让cat去调用另一个方法
    anInvocation.target = [Cat new];
    anInvocation.selector = @selector(test1);
    [anInvocation invoke];

    // - 类方法
    anInvocation.target = [Cat class];
    anInvocation.selector = @selector(test1);
    [anInvocation invoke];
    
    // - 带参数的方法
    anInvocation.target = [Cat new];
    anInvocation.selector = @selector(test1);
    
    int age = 0;
    int hei = 0;
    [anInvocation getArgument:&age atIndex:2];
    [anInvocation getArgument:&hei atIndex:3];
    [anInvocation setArgument:&age atIndex:2];
    [anInvocation setArgument:&hei atIndex:3];
    [anInvocation invoke];
    
    int result = 0;
    [anInvocation getReturnValue:&result];
}