解决timer和block循环引用

#import "ViewController.h"

typedef void(^Block)(void);

@interface ViewController ()

@property(nonatomic,strong)Block block1;

@property(nonatomic,strong)Block block2;

@property(nonatomic,strong)NSTimer *timer;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    [self circularReference1];

    [self circularReference2];

    [self circularReference3];

    [self circularReference4];

    [self circularReference5];

}

#pragma mark - 必须在控制器返回前停掉计时器，打破循环引用，可正常释放

- (void)circularReference1 {

    //    self.timer = [NSTimer timerWithTimeInterval:1 target:self selector:@selector(testName) userInfo:nil repeats:YES];

    //    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];

        //上面两句等同于下面一句 scheduled会自动将timer加入主循环并自动开启计时器

        self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(testName) userInfo:nil repeats:YES];

}

- (void)viewDidDisappear:(BOOL)animated {

    [superviewDidDisappear:animated];

    [self.timer invalidate];

    self.timer=nil;

}

#pragma mark - 只需将任务中的self替换成weakSelf

- (void)circularReference2 {

    __weaktypeof(self) weakSelf =self;

    [NSTimer scheduledTimerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {

        [weakSelftestName];

    }];

}

#pragma mark - 局部变量block1不会造成循环引用

- (void)circularReference3 {

    Blockblock1 = ^ {

        NSLog(@"= %@",self);

    };

    block1();

}

#pragma mark - 使用__block修饰weakSelf，但是限制条件多

- (void)circularReference4 {

    __blockidweakSelf =self;

    self.block1= ^ {

        NSLog(@"= %@",weakSelf);

        weakSelf =nil;//这里必须设置为nil，否则还是不能释放

    };

    self.block1();//这里必须调用，否则还是不能释放

}

#pragma mark - 使用__weak修饰weakSelf

- (void)circularReference5 {

    __weaktypeof(self) weakSelf =self;

    self.block2= ^ {

        NSLog(@"== %@",weakSelf);

    };

    self.block2();

}

- (void)testName {

    NSLog(@"%@",self);

}

- (void)dealloc {

    NSLog(@"%s",__func__);

}