Calling [self methodName] from inside a block? - objective-c

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.

Answer 2

The accepted answer is outdated. Using __block in that case can cause errors!
To avoid this problem, it’s best practice to capture a weak reference to self, like this:
- (void)configureBlock {
XYZBlockKeeper * __weak weakSelf = self;
self.block = ^{
[weakSelf doSomething]; // capture the weak reference
// to avoid the reference cycle
}
}
Please, look at Apple Documentation - Avoid Strong Reference Cycles when Capturing self
for more details.

Answer 3

__block CURRENTViewController *blocksafeSelf = self;
[homeHelper setRestAsCheckIn:strRestId :^(NSObject *temp) {
[blocksafeSelf YOURMETHOD:params];
}];

Answer 4

Is it possible to call a method [self methodName] from within a block?
Yes, why not. If your tempFunction is an instance method, you can do it. The called method should be accessible is the only restriction.

Answer 5

Consider this (which I think is the best practice)
#implementaion ViewController
- (void) viewDidLoad {
__weak typeof(self) wself = self;
[xxx doSomethingUsingBlock: ^{
__strong typeof(wself) self = wself;
[self anotherMessage];
}];
}
#end
Moreover, You can define wrapper macros.
#define MakeWeakSelf __weak typeof(self) wself = self
#define MakeStrongSelf __strong typeof(wself) self = wself

Answer 6

I wonder whether you [fader setFunction:tempFunction]; then is synchronous or asynchronous.
blocks push onto stack.so in MRR,if you don't retain it,it will pop off.
-(void)someFunction{
Fader* fader = [[Fader alloc]init];
void (^tempFunction)(void) = ^ {
[self changeWindow:game];
//changeWindow function is located in superclass
};
[fader setFunction:tempFunction];
//if the tempFunction execute there will be right.
}//there the tempFunction pop off
//....some thing go on
//execute the tempFunction will go wrong.