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Re: null selector

Subject: Re: null selector
From: Ryan Britton <email@hidden>
Date: Wed, 14 Sep 2005 06:55:12 -0700
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On Sep 14, 2005, at 4:48 AM, Keith Alperin wrote:

Greetings Cocoa-Devs!
I'm trying to implement a callback using an NSInvocation. However, when i call invoke, i get: "<NSInvalidArgumentException> *** - [MyTestApp methodSignatureForSelector:]: null selector".
Here is some test code that I am using:
- (void)awakeFromNib {
    SEL *handlerSelector = @selector(someMethod: otherArg:);


The value @selector returns is not a pointer.

NSMethodSignature *signature = [self methodSignatureForSelector: handlerSelector]; NSInvocation *handler = [NSInvocation invocationWithMethodSignature: signature]; [handler setTarget:self]; [handler retain]; int *someArg = 1; int *otherArg = 2; [handler setArgument:&someArg atIndex:2]; [handler setArgument:&otherArg atIndex:3];

Here you're passing int pointers to a method that expects normal ints. Removing the pointer aspect of int *someArg and int *otherArg should fix that.

[handler invoke];

You need to do setSelector: on handler as well before you invoke it. Both that setting and the method signature are absolute requirements when using NSInvocation.

}
- (void)someMethod:(int)someArg otherArg:(int)otherArg {
    NSLog("keyCode=%d",someArg);
    NSLog("modifierFlags=%d",otherArg);
}
the "someMethod" method is declared in the header file. The error occurs when calling [handler invoke].

Does anyone out there in cocoa land see the problem? This feels like a rookie mistake, but as a cocoa rookie, I can't really tell what that is.
Many thanks,
Keith R. Alperin
kalperin mac com
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References:
	>null selector (From: Keith Alperin <email@hidden>)

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