block的循环引用

1、创建block用copy修饰，拷贝到堆上

2、之前一直用这种写法，但会碰到提前释放的状态

__weak typeof(self)wakeself = self;

3、就用弱指针指向self，在block内部对weakSelf产生一个强引用，就解决了提前释放的问题

@weakify(self);

@strongify(self);

例如：

__weak __typeof(self) weakSelf = self;
self.block = ^{
    __strong __typeof(weakSelf) strongSelf = weakSelf;
    [strongSelf doSomething1];
    [strongSelf doSomething2];
}

或者

#define WEAKSELF __weak typeof(self)weakSelf =self

#define StrongSelf __strong typeof(weakSelf) strongSelf = weakSelf

使用：

WEAKSELF;

[_cell setBurstBlock:^(NSInteger leftTag) {

StrongSelf;

[strongSelf showNavigationView:[GoodsViewController new]];

}];