使用performSelector时发生崩溃：使用从另一个类传递的SEL [英] Crash when using performSelector: with a SEL passed from another class

问题描述

是否可以向另一个类发送一个选择器，并在另一个类上执行？

Is it possible to send a selector to another class and have it perform on that other class?

这似乎与错误 ***由于未捕获异常NSInvalidArgumentException终止应用程序，原因：' - [webManager _selector]：无法识别的选择器发送到实例。如果这是不可能的，你会推荐什么作为替代？

This seems to crash with the error *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[webManager _selector]: unrecognized selector sent to instance. If this is not possible, what would you recommend as an alternative?

方法是按照它们执行的顺序放置。

The methods are placed in the order that they are performed.

//in HomeViewController
-(void)viewDidLoad
{
    WebManager *webManager = [[WebManager alloc] init];
    URLCreator *urlCreator = [[URLCreator alloc] initWithParam:@"default"];
    [webManager load:[urlCreator createURL] withSelector:@selector(testSelector)];
}
//in WebManager, which is also the delegate for the URL it loads when the load method is called...
-(void)load:(NSString*)url withSelector:(SEL)selector
{
    _selector = selector;    
    [self load:url];
}

-(void)load:(NSString*)url{
    NSURLRequest * request = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:url]];
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [connection start];
}

//now the delegate response, ALSO in WebManager
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
    NSLog(@"Connection did finish loading. Parsing the JSON");

    [self getJSONDict:rawData]; //parses the data to a dictionary

    //perform the selector that is requested if there is one included
    if (_selector)
    {
        NSLog(@"Performing selector: %@", NSStringFromSelector(_selector));
        //the selector is called testSelector
        [self performSelector:@selector(_selector)];    
    }
}

- (void)testSelector //also in the WebManager class
{
    NSLog(@"Selector worked!");
}

推荐答案

/ p>

This is your problem:

[self performSelector:@selector(_selector)];

A SEL 的方法。 @selector 是一个编译器指令，它将括号内的文本文本转换为 SEL 。

A SEL is a type representing the name of a method. @selector is a compiler directive which converts the literal text inside the brackets into a SEL.

但是 _selector ，您的ivar已经包含 SEL 。您正在将文本_selector转换为 SEL ，然后尝试使用它。因为在目标类中没有使用选择器_selector的方法，所以会出现异常。

But _selector, your ivar, already contains a SEL. You're converting the text "_selector" into a SEL, and then trying to use that. Since no method with the selector "_selector" exists in the target class, you get an exception.

将行更改为：

[self performSelector:_selector];

，一切都应该dandy。这使用已经存储在变量 _selector 中的 SEL 。

and everything should be dandy. This uses the SEL which you already have stored in the variable _selector.

_{此外，一般来说，请先张贴您的实际代码。}

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