iOS block 。如何从 block setter 中引用对象实例？

Question

我有一个对象，其属性指向一个 block :

typedef void (^ThingSetter)();
@property(nonatomic, strong) ThingSetter setup;

我用 block 初始化属性。在 block 中，我引用了对象实例:

Thing *thing = [[Thing alloc] init];

thing.setup = ^() {

    plainOleCFunction(thing.number);
    [thing doSomethingWithString:@"foobar"];
};

但是我收到关于保留循环的编译警告:

capturing 'thing' strongly in this block is likely to lead to a retain cycle
block will be retained by the captured object

正确的做法是什么？

谢谢，道格

Answer 1

你必须将 thing 指定为弱引用:

Thing *thing = [[Thing alloc] init];
__weak Thing *weakThing = thing;

thing.setup = ^() {

    plainOleCFunction(weakThing.number);
    [weakThing doSomethingWithString:@"foobar"];
};

或者您可以提供 thing 作为 block 的参数:

Thing *thing = [[Thing alloc] init];

thing.setup = ^(Thing *localThing) {

    plainOleCFunction(localThing.number);
    [localThing doSomethingWithString:@"foobar"];
};
thing.setup(thing);