executing blocks stored in NSMutableArray with a parameter

Question

I'm trying to understand blocks a bit more.

I have these definitions:

@property (nonatomic, retain) NSMutableArray * callBacksOnSuccess;
@property (nonatomic, copy) void (^callBackSuccessWithUIImage) (UIImage *) ;

When the image download finishes I do this in the completion block and things are fine

UIImage *coverImage = [UIImage imageWithData:data];
callBackSuccessWithUIImage(coverImage);

Now I'd like to be able to do same for all callback blocks stored in the callBacksOnSuccess NSMutableArray but I don't know how to approach this.

I'm trying a for in loop, but that's not working most likely because of the ambigous id class definition:

UIImage *coverImage = [UIImage imageWithData:data];
for (id callBackBlock in callBacksOnSuccess) 
{callBackBlock(coverImage);}

Please push me towards the right approach.

thank you!

Lucas Eduardo · Accepted Answer · 2013-09-04 13:09:17Z

3

First of all:

Consider to use a typedef to your blocks, in order to ease the syntax:

typedef void (^MyBlock)(UIImage*); //declare this somewhere

Then, you can easily iterate through your array like this, executing each block inside it:

UIImage *coverImage = [UIImage imageWithData:data];
for (MyBlock block in callBacksOnSuccess) {
    block(coverImage);
}

You can even use the new type in your property:

@property (nonatomic, copy) MyBlock callBackSuccessWithUIImage;

edited Sep 4, 2013 at 13:09

answered Sep 4, 2013 at 1:57

Lucas Eduardo

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3 Comments

EarlGrey Over a year ago

thank you! works like a charm. so surprised to see typedef as the solution.

Lucas Eduardo Over a year ago

Glad to help! The typedef actually just made everything much easier to understand and read. Your problem was because you were declaring the callBackBlock variable inside the foreach loop as the type of id, who does not support calls like block(). If you had declared the variable as void (^callBackBlock) (UIImage *) in the for loop, it would have worked in the same way, but just a lot 'uglier'

EarlGrey Over a year ago

yes, I knew the id was the problem, just couldn't figure out what to do about it. Blocks are awesome, I just need a bit more time to understand them fully.

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