Question

I’ve just run into blocks and I think they are just what I’m looking for, except for one thing: is it possible to call a method [self methodName] from within a block?

This is what I’m trying to do:

-(void)someFunction{
    Fader* fader = [[Fader alloc]init];

    void (^tempFunction)(void) = ^ {
        [self changeWindow:game]; 
        //changeWindow function is located in superclass
    };

    [fader setFunction:tempFunction];
}

I’ve been searching for a couple of days and I can’t find any evidence that this is possible.

Is this at all possible, or am I trying to use blocks for something they aren’t meant for?

The reason I’m using blocks is that I’ve created a Fader class, and I want to store a block for it to execute when it finishes fading out.

Thank you

EDIT:
Okay, I added in the suggestion, but I’m still getting an EXC_BAD_ACCESS error…

-(void)someFunction{
    Fader* fader = [[Fader alloc]init];

    __block MyScreen* me = self;

    void (^tempFunction)(void) = ^ {
        [me changeWindow:game]; 
        //changeWindow function is located in superclass
    };

    [fader setFunction:tempFunction];
    [fader release];
}

Maybe I’m not allowed to give fader the function…?

Answer 1

Yes, you can do this.

Note, however, that the block will retain self. If you end up storing this block in an ivar, you could easily create a retain cycle, which means neither would ever get deallocated.

To get around this, you can do:

- (void) someMethodWithAParameter:(id)aParameter {

  __block MySelfType *blocksafeSelf = self;
  void (^tempFunction)(void) = ^ {
      [blocksafeSelf changeWindow:game];
  };

  [self doSomethingWithBlock:tempFunction];

}

The __block keyword means (among other things) that the referenced object will not be retained.