What does __weak it mean exactly?

Question

I am (trying to) learn Objective-C and I keep coming across a phrase like:

__weak IBOutlet NSLayoutConstraint *webViewLeftConstraint;

What does __weak it mean exactly in Objective-C? Why we need to put __(underscore twice) in variable? Can we use only one time? like( _ ) other declaration in other language..

http://stackoverflow.com/questions/11773342/what-is-the-difference-between-a-weak-and-a-block-reference — user681574, Mar 16 '17 at 03:53
.. or you could take a look at the Wikipedia article on "weak reference". — GlennRay, Mar 16 '17 at 03:59

score 1 · Answer 1 · answered Mar 16 '17 at 05:20

1

If the outlet is referencing a UI Object in the View hierarchy then you should make it weak as the view hierarchy already has a strong reference.

Weak is specifically needed to avoid a retain cycle.

answered Mar 16 '17 at 05:20

Arpit Jain

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What does __weak it mean exactly?

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