Capturing a variable in a Block when the Block is in the initializer

Question

Consider this:

id observer = [[NSNotificationCenter defaultCenter] 
    addObserverForName:MyNotification 
                object:nil 
              


        

Answer 1

As explained in the answers to

Why doesn't Remove Observer from NSNotificationCenter:addObserverForName:usingBlock get called,

you have to

• add __block, so that the block will refer to the initialized variable, AND
• add __weak, to avoid a retain cycle. (The latter applies only to ARC. Without ARC, the block does not create a strong reference to a __block variable.)

Therefore:

__block __weak id observer = [[NSNotificationCenter defaultCenter] ...