objc_msgSend()实现
3. 消息转发：__forwarding__
- (id)forwardingTargetForSelector:(SEL)aSelector
{
if (aSelector == @selector(test)) {
// objc_msgSend([[Cat alloc] init], aSelector)
return [[Cat alloc] init];
}
return [super forwardingTargetForSelector:aSelector];
}
//方法签名：返回值类型、参数类型
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
if (aSelector == @selector(test)) {
return [NSMethodSignature signatureWithObjCTypes:"v@:"];
}
return [super methodSignatureForSelector:aSelector];
}
/**NSInvocation封装了一个方法调用，包括：方法调用者、方法名、方法参数
anInvocation.target 方法调用者
anInvocation.selector 方法名
[anInvocation getArgument:NULL atIndex:0]
*/
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
[anInvocation invokeWithTarget:[[Cat alloc] init]];
}
