Avoid a circular reference to a block

Avoid block circular references what is a circular reference, when a circular reference occurs

1 A circular reference is when self has a block, and the method of self is called at block. Form you have me, I have you, who can not release who the dilemma.

self.myBlock = ^{    [self doSomething];  };       +-----------+           +-----------+       |    self   |           |   Block   |  ---> |           | --------> |           |       | retain 2 | <-------- | retain 1 | | | | | +-----------+ +-----------+

Or

ClassA* objA = [[[ClassA alloc] init] autorelease];  objA.myBlock = ^{    [self doSomething];  };  self.objA = objA;  +-----------+           +-----------+           +-----------+  |   self    |           |   objA    |           |   Block   |  |           | --------> |           | --------> |           |  | retain 1  |           | retain 1  |           | retain 1  |  |           |           |           |           |           |  +-----------+           +-----------+           +-----------+       ^                                                |       |                                                |       +------------------------------------------------+

This is the official explanation at the time.
The general meaning is that, for example, Self has a button, and you have to invoke something in the button setting.

［self.button  ^｛ }］

So far, there's no problem, but for some reason, you're going to call it in this block again.
Self.label.text = @ "I am Label";
That's it.

［self.button  ^｛      self.label.text = @"I am Label"; }］;//这个时候就变成这样了。 +-----------+ +-----------+ +-----------+ | self | | button | | Block | | | --------> | | --------> | | | retain 1 | | retain 1 | | retain 1 | | | | | | | +-----------+ +-----------+ +-----------+ ^ | | | +------------------------------------------------+

The general understanding is this, if there are deviations, please point out.

Workaround

In short, just one sentence:

__weak typeof (self) weakSelf = self;

For example, the above example, as follows.

 __weak typeof (self) weakSelf = self;［self.button ^｛ weakSelf.label.text = @"I am Label"; }］;//这个时候就变成这样了。 +-----------+ +-----------+ +-----------+ | self | | button | | Block | | | --------> | | --------> | | | retain 1 | | retain 1 | | retain 1 | | | | | | | +-----------+ +-----------+ +-----------+ ^ | | | + - - - - - - - - - - - - - - - - - - - - - - - -+ weak

Avoid a circular reference to a block