Runtime消息转发机制

一.消息转发机制

    void sendMessage(idself,SEL_cmd,NSString* msg){

        NSLog(@"1===hello");

    }

  1.动态方法解析（resolveInstanceMethod）

    + (BOOL)resolveInstanceMethod:(SEL)sel{

          if([NSStringFromSelector(sel) isEqualToString:@"sendMessage:"]){

           returnclass_addMethod(self, sel, (IMP)sendMessage,"v@:@");

        }

        return NO;

    }

  2.快速转发（forwardingTargetForSelector）

    - (id)forwardingTargetForSelector:(SEL)aSelector{

        NSString* methodName =NSStringFromSelector(aSelector);

        if([methodNameisEqualToString:@"sendMessage:"]){

            return[MessageObjectnew];

        }

        return [super forwardingTargetForSelector:aSelector];

    }

  3.慢速转发

    方法1.methodSignnatureForSeletor

    方法2.forwardinvocation

    - (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{

        NSString*methodName =NSStringFromSelector(aSelector);

        if([methodNameisEqualToString:@"sendMessage:"]){

        return [NSMethodSignature signatureWithObjCTypes:"v@:@"];

    }

        return [super methodSignatureForSelector:aSelector];

    }    

    - (void)forwardInvocation:(NSInvocation*)anInvocation{

        SELsel = [anInvocationselector];

        MessageObject *object = [MessageObject new];

        if([objectrespondsToSelector:sel]){

            [anInvocationinvokeWithTarget:object];

        }else{    

            [superforwardInvocation:anInvocation];    

        }

    }

  4.方法没实现调用

  doesNotRecognizeSelector

- (void)doesNotRecognizeSelector:(SEL)aSelector{

    NSLog(@"方法未实现");

}