相关疑难解决方法(0)

我正在使用MacOS-X 10.6.7和Xcode 4.0.2上的Objective-C中的respondsToSelector方法来识别对象是否会响应某些消息.根据手册,NSString不应该响应appendString:而NSMutableString应该.这是测试它的代码片段:

int main (int argc, const char * argv[])
{

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    NSString *myString = [[NSString alloc] init];

    if ([myString respondsToSelector:@selector(appendString:)]) {
        NSLog(@"myString responds to appendString:");
    } else {
        NSLog(@"myString doesn't respond to appendString:");
    }

    // do stuff with myString

    [myString release];
    [pool drain];
    return 0;
}

这是输出:

Class02[10241:903] myString responds to appendString:

我有点期待相反的事情.NSString对象如何响应appendString:这里发生了什么,我失踪了？