PerformSelector warning

问题:

I'm receiving a warning

PerformSelector may cause a leak because its selector is unknown

In the code:

- (void) callDelegate: (SEL) selector withArg: (id) arg error: (NSError*) err
{
    assert([NSThread isMainThread]);
    if([delegate respondsToSelector: selector])
    {
        if(arg != NULL)
        {
            //this line the warning
            [delegate performSelector: selector 
                           withObject: arg 
                           withObject: err]; 
        }
        else
        {
            //this line the warning
            [delegate performSelector: selector 
                           withObject: err]; 
        }
    }
    else
    {
        NSLog(@"Missed Method");
    }
}

Header:

@interface Topscore : UIViewController <NSObject> {

//
}

回答1:

This is a warning generated by the compiler because -Wundeclared-selector was used while compiling and automatic reference counting (ARC) is enabled. This can be, in general, safely ignored, as it's obvious that the selector in the variable named "selector" is unknown at compile time, as it will have its value assigned at runtime.

回答2:

Your if ... respondsToSelector: selector won't work because your selector is just the name of the method. For your case you need to check

if ([delegate respondsToSelector: @selector(method::)]

and for the other case just for method:.

Anyway, you can supress the warning like this:

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
    [self performSelector:nextView];
#pragma clang diagnostic pop

回答3:

You can also use objc_msgSend instead of performSelector, as described here.

回答4:

You could add -Wno-arc-performSelector-leaks for WARNING_CFLAGS in the Build Settings.

Found the solution here

回答5:

Easiest way is adding this macro to your pch File. Or .m file..

#pragma GCC diagnostic ignored "-Wundeclared-selector"