Question

I’m getting a EXC_BAD_ACCESS exception when I call performSelector:withObject: from a object that does implement the method I’m trying to call. Here’s my code

SEL newSelector = NSSelectorFromString(@"mySelector:withCustomObject:");
[self performSelector:newSelector withObject:myCustomObject];

This causes a crash. However when I do this

[self performSelector:@selector(mySelector:withCustomObject:) withObject:myCustomObject];

it works.

Any ideas on why this is happening?
PS: none of the parameters are nil.

MORE CODE:

// My code to call this method
SEL newSelector = NSSelectorFromString(@"mySelector:withCustomObject:");
[self performSelector:newSelector withObject:self withObject:myCustomObject];

// this code is NOT called.
- (void) mySelector:(jObject *)sender withCustomObject:(jEvent *)customObject
{
    NSDictionary *handlerData = [aProperty objectAtIndex:[event positionInMethodStack]];
    NSString *newTitle = [handlerData objectForKey:@"newTitle"];
}

Answer 1

"mySelector:withCustomObject:" is the signature of a method with 2 arguments, such as

- (void)mySelector:(id)firstArgument withCustomArgument:(id)secondArgument { ... }

But you call performSelector:withObject:, which sends a message with only one argument to mySelector. The second argument is undefined, which probably causes the crash.

So if mySelector actually has 2 arguments, use performSelector:withObject:withObject:, otherwise fix the signature of the selector.