NSTimer Category + Blocks implementation to replace selector

Question

I am quite new to blocks and objective-c, and i am trying to write my first category using both. My idea is to create a category on NSTimer that will receive a block as a pa

Answer 1

Your major flaw besides the wrong target is your use of a static variable. You won't be able to support beyond a single timer.

Using block as argument to the invoked method.

@interface NSTimer (AdditionsPrivate) // Private stuff
- (void)theBlock:(VoidBlock)voidBlock;
@end


@implementation NSTimer (NSTimer_Additions)

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)theSeconds repeats:(BOOL)repeats actions:(VoidBlock)actions {
    NSInvocation * invocation = [NSInvocation invocationWithMethodSignature:[self instanceMethodSignatureForSelector:@selector(theBlock:)]];
    NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:theSeconds
                                                   invocation:invocation
                                                      repeats:repeats];
    [invocation setTarget:timer];
    [invocation setSelector:@selector(theBlock:)];
    
    Block_copy(actions);
    [invocation setArgument:&actions atIndex:2];
    Block_release(actions);

    return timer;
}


- (void)theBlock:(VoidBlock)voidBlock {
    voidBlock();
}

@end

The problem with using associative references was the leak as there was no good point to release the block.

---

Earlier Approach using associative references

You can use associative references to attach the block to that particular instance of NSTimer.

@implementation NSTimer (NSTimer_Additions)

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)theSeconds repeats:(BOOL)repeats actions:(VoidBlock)actions {
    NSInvocation * invocation = [NSInvocation invocationWithMethodSignature:[self instanceMethodSignatureForSelector:@selector(theBlock)]];
    NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:theSeconds
                                                   invocation:invocation
                                                      repeats:repeats];
    [invocation setTarget:timer];
    [invocation setSelector:@selector(theBlock)];

    objc_setAssociatedObject(timer, @"Block", actions, OBJC_ASSOCIATION_COPY);
    
    return timer;
}


- (void)theBlock {
    VoidBlock _voidBlock = (VoidBlock)objc_getAssociatedObject(self, @"Block");
    _voidBlock();
}

@end