Capturing 'self' strongly in this block is likely to lead to a retain cycle [duplicate]

//日期回调

   **__weak typeof(self) weakSelf = self;**    datePickVC.completeBlock = ^(NSString *selectDate) {    [**weakSelf.**starDataBtn setTitle:selectDate forState:UIControlStateNormal];    weakSelf.starDataBtn.backgroundColor = [UIColor redColor];    };

You should review your block for:
(a) any explicit references to self
(b) any implicit references to self caused by referencing any instance variables.

Let’s imagine that we have some simple class property that was a block (this will experience the same “retain cycle” warnings as your question, but will keep my examples a little simpler):

@property (nonatomic, copy) void (^block)(void);

And let’s assume we had some other class property we wanted to use inside our block:

@property (nonatomic, strong) NSString *someString;

If you reference self within the block (in my example below, in process of accessing this property), you will obviously receive that warning about the retain cycle risk:

self.block = ^{
NSLog(@”%@”, self.someString);
};

That is remedied via the pattern you suggested, namely:

__weak typeof(self) weakSelf = self;

self.block = ^{
NSLog(@”%@”, weakSelf.someString);
};

Less obvious, you will also receive the “retain cycle” warning if you reference an instance variable of the class inside the block, for example:

self.block = ^{
NSLog(@”%@”, _someString);
};

This is because the _someString instance variable carries an implicit reference to self, and is actually equivalent to:

self.block = ^{
NSLog(@”%@”, self->_someString);
};

One might be inclined to just use weakSelf pattern again, resulting in the weakSelf->_someString syntax, but the compiler will warn you about this:

Dereferencing a __weak pointer is not allowed due to possible null value caused by race condition, assign it to strong variable first

You therefore resolve this by using the weakSelf pattern, but also create a local strong variable within the block and use that to dereference the instance variable:

__weak typeof(self) weakSelf = self;

self.block = ^{
__strong typeof(self) strongSelf = weakSelf;

if (strongSelf) {    NSLog(@"%@", strongSelf->_someString);    // or better, just use the property    //    // NSLog(@"%@", strongSelf.someString);}

};