How to write a completion block in objective-C?

Question

I'm having trouble creating completion blocks. I found the solution here . It works for me, but I don't quite understand this. Now I'm still confused and don't know how to write a block myself. Are there any batter ways to understand blocks? Also, when should I use it? Is there anything that can replace blocks?

Should I create it as a property? Method perimeter? Do they have difference in efficiency?

Thank you!

What do you need to know? How to write a method that takes a block? How to pass a block to a method? — Rengers, Jan 05 '15 at 16:52
this kind of question is too broad, you aren't asking a specific question even about syntax, or presenting a problem — Grady Player, Jan 05 '15 at 16:52
That's what makes me confused. I don't know how to create a block. Beginner in blocks :( — NSError, Jan 05 '15 at 16:53

score 2 · Accepted Answer · answered Jan 05 '15 at 16:53

2

check out http://fuckingblocksyntax.com for syntax. For personal choice I like to return value and error in the completion block (similar to iOS framework pattern) As an example;

declaration

- (void)fetchStuff:(void (^)(id value,NSError *error))completion;

calling the function

// async fetch
[object fetchStuff:^(id value, NSError *error) {
    // do stuff with value
}];

answered Jan 05 '15 at 16:53

cekisakurek

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What's the difference between a block as a perimeter and block as property? Do they have difference in efficiency? – NSError Jan 05 '15 at 18:31
I think it is safe to say they are both same. But I am not really sure. – cekisakurek Jan 06 '15 at 15:07

How to write a completion block in objective-C?

1 Answers1