關於block 循環引用 weakSelf

block代碼塊裏用到的東西，比如主線程裏的全局變量，局部變量，UI等，block都會對它指向一個strong指針。也就是說，局部變量所在的局部代碼運行完後，局部變量不會釋放，直到block消失，它才釋放。

 

這個不太好，這樣如果block代碼裏面有self.something，而block又存儲在strong的全局變量裏，會導致block對self一個strong指針，self對block又有一個strong指針，就導致了memory circle。相應的解決辦法是：

__weak MyClass *weakself = self;

使得block指向self一個弱指針。self指向block仍舊是強指針。這樣一個是弱的便解決問題了。

#import "ViewController.h"
typedef void(^MyBlock)();

@interface ViewController ()

@property (nonatomic,copy) MyBlock block;
@property (nonatomic,copy) NSString *name;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    
    __weak typeof(self) weakself = self;
    self.block = ^{
        weakself.name = @"block";
    };
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end