$ 问题抛出来

1.所有自定义方法的block都需要__weak 吗?
2.凡是, block内带 self的都需要 __weak 吗?
3.凡是, 系统方法中的block, 都不需要__weak 吗?

  看看上述问题的反问语气, 相必语文过关的同学们都知道答案,一看就是 No No No ~         
  -> 😄 恭喜你~ right !

$ but why ?

至于原因 👇

想必大伙都知道, 互相strong持有成了一个环 , 然后就无法释放了~

$ block 常见场景(暂时想到的一些情况, 后续想到继续补充)

first, code准备:
👇 一个子View -- TestOneView, 创建各种参数为block的方法

 //  TestOneView.h
 #import <UIKit/UIKit.h>

 typedef void(^ZYOneBlock1)();

 typedef void(^ZYOneBlock2)();

 @interface TestOneView : UIView
 // copy修饰 
 @property (nonatomic,   copy)     ZYOneBlock1 oneBlock;
 // weak修饰
 @property (nonatomic,   weak)     ZYOneBlock1 weak_oneBlock;
 
 // 持有 传入的block , 但是 weak
 - (void)testWeakBlock:(ZYOneBlock1) block;

 // 不持有 传入的block , 在method中直接执行掉
 - (void)testBlock2WithBlock:(ZYOneBlock2) secondblock;

 @end

  // TestOneView.m
  #import "TestOneView.h"

  @implementation TestOneView

  /*
  // Only override drawRect: if you perform custom drawing.
  // An empty implementation adversely affects performance during animation.
  - (void)drawRect:(CGRect)rect {
      // Drawing code
  }
  */

  // 持有 传入的block , strong
  -(void)setOneBlock:(ZYOneBlock1)oneBlock{
      
      _oneBlock = oneBlock;
      _oneBlock();
  }

  // 持有 传入的block , 但是 weak
  - (void)testWeakBlock:(ZYOneBlock1) block;
  {
      self.weak_oneBlock = block;
  }

  // 不持有 传入的block , 在method中直接执行掉
  - (void)testBlock2WithBlock:(ZYOneBlock2) secondblock;
  {
      secondblock();
  }
  
  // 通过dealloc 检测能否释放
  -(void)dealloc{
      NSLog(@"%s",__func__);
  }

  @end

go on ~ , code一个被push的VC -- TestOneViewController , 即是 block纵横所在的江湖

😏😏😏 block 出场 😏😏😏

• <1> A 操作 B的bloc

  (1).传给子View的block被子view 👉strong持有 , block块中使用了_ivar(成员变量) 、strong property , 处理方式如下:

    - (void)testStrongBlock_1{
        [self.view addSubview: self.oneView];
  
        __weak typeof(self) weakSelf = self;
        self.oneView.oneBlock = ^{
            __strong typeof(weakSelf) strongSelf = weakSelf;
            strongSelf->_intType = 11;
            strongSelf.pArray = @[@(11)];
        };
    }
  

  (2).传入的block块中 含有本类的实例方法

  - (void)testMethod_StrongBlock_1{
        
        [self.view addSubview: self.oneView];
        
        __weak typeof(self) weakSelf = self;
        self.oneView.oneBlock = ^{
            __strong typeof(weakSelf) strongSelf = weakSelf;
  
            // method
            [strongSelf containSelfMethod];
        };
    }
    - (void)containSelfMethod{
        _intType = 1010;
        self.pArray = @[@(2020)];
    }
  

  (3).传给子view的block 被子view 👉weak持有, 在方法内被执行完。 无需weakSelf

  - (void)testWeakBlock_1{
        
        [self.view addSubview: self.oneView];
        
        [self.oneView testWeakBlock:^{
            _intType = 111;
            self.pArray = @[@(1)];
        }];
    }
  

  (4).传给子view的block ❌不 被子view 持有, 直接执行掉。 无需weakSelf

    - (void)testParamBlock_2{
        
        [self.view addSubview: self.oneView];
        
        [self.oneView testBlock2WithBlock:^{
            _intType = 22;
            self.pArray = @[@(1)];
        }];
    }
  

• <2> A 操作 A的block

  (a).block作参数, ❌不 被持有

    - (void)testParam_SelfBlock_1{
        [self testParam_SelfBlcokWith:^(NSArray * arr) {
            self.pArray = arr;
            NSLog(@"%s",__func__);
        }];
    }
    - (void)testParam_SelfBlcokWith:(MyBlockOne)myBlock{
        
        NSArray * arr = @[@"myblock1"];
        myBlock(arr);
        
    }
  

  (b).block作参数, 👉被持有

    - (void)testCopy_SelfBlock_1{
        
            __weak typeof(self) weakSelf = self;
        [self testCopy_SelfBlcokWith:^(NSArray * arr) {
            __strong typeof(weakSelf) strongSelf = weakSelf;
            
            strongSelf.pArray = arr;
            NSLog(@"%s",__func__);
        }];
    }
    - (void)testCopy_SelfBlcokWith:(MyBlockOne)myBlock{
        
        self.myBlock1 = myBlock;
        
        NSArray * arr = @[@"myblock1"];
        
        NSLog(@"%s",__func__);
        sleep(1);
        NSLog(@"%s",__func__);
        self.myBlock1(arr);
    }
  

• <3> GCD的block(系统的) 无需weakSelf 。注意: GCD延时block, 会使VC pop后延迟释放

    - (void)didMoveToParentViewController:(UIViewController *)parent{
        
        [self.oneView removeFromSuperview];
        
        NSLog(@"%s , %@",__func__ ,self);
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            
            NSLog(@"%s , %@",__func__ ,self);
            [self testBackTimerAfter];  // 点击pop 时,会延迟2s dealloc
            
        });
    }
      - (void)testBackTimerAfter{
           
        [self.oneView testWeakBlock:^{
            NSLog(@"%s , %@",__func__ ,self);
        }];
        
        __weak typeof(self) weakSelf = self;
        _oneView.oneBlock = ^{
            __strong typeof(weakSelf) strongSelf = weakSelf;
            NSLog(@"%s , %@",__func__ ,strongSelf);
        };
    }
  

• <4> ☺补充☺, 对于NSTimer addTarget: self...

  _weak typeof(self) weakSelf = self;
  _timer = [NSTimer scheduledTimerWithTimeInterval:3.0f
                                            target:weakSelf
                                          selector:@selector(timerFire:)
                                          userInfo:nil
                                           repeats:YES];
  

  对于如上解决方式, 是有误的,详解 可参考 👉 解决NSTimer/CADisplayLink的循环引用

超懒人 点击 github demo 下载 调试 。
祝愿有所收获哦 ~ ^_ ~