块后BAD ACCESS一个块内被调用（IOS）(BAD ACCESS after block wi

我在那里，我从火力检查用户的状态属性块。如果状态属性是“自由”我想从块返回，否则我想搜索其他用户，并检查他们的状态和这样做，直到一个“自由”的用户已经发现：

void( ^ myResponseBlock)(BOOL finished) = ^ void(BOOL finished) {

if (finished) {
    if ([self.freedom isEqualToString: @"free"]) {
        NSLog(@"free!");
        return;
    } else if ([self.freedom isEqualToString: @"matched"]) {
        NSLog(@"get another user");
        //get another user
        do {
            //picking another random user from array
            rando = arc4random_uniform(arraycount);
        }

        while (rando == randomIndex && rando == [self.randString intValue]);
        self.randString = [NSString stringWithFormat: @"%u", rando];
        [users removeAllObjects];
        [users addObject:usersArray[rando]];
        self.freeUser = users.firstObject;

        NSLog(@"set up another check");

        //error is called after this block is called here, again
        [self checkIfFree: myResponseBlock];

    } else {
        NSLog(@"error!");
    }
} else {
    NSLog(@"not finished the checking yet");
}
};
[self checkIfFree: myResponseBlock];

如图所示，我发现了“BAD ACCESS”的错误，当块被调用用于在第二时间“compblock（YES）”行以下：

-(void)checkIfFree:(myCompletion) compblock{

self.freeUserFB = [[Firebase alloc] initWithUrl:[NSString stringWithFormat: @"https://skipchat.firebaseio.com/users/%@", self.freeUser.objectId]];

[self.freeUserFB observeEventType:FEventTypeValue  withBlock:^(FDataSnapshot *snapshot)
 {
     self.otherStatus = snapshot.value[@"status"];

     NSLog(@"snapshot info %@", snapshot.value);

     if ([self.otherStatus isEqualToString:@"free"]) {
         self.userIsFree = YES;
         self.freedom = @"free";
         NSLog(@"user is free in the check method %@", self.freedom);
     }
     else{
         self.userIsFree = NO;
         self.freedom = @"matched";
         NSLog(@"user is matched in the check method %@", self.freedom);

     }
     compblock(YES);
 }];
}

一切都很好，如果块没有被召回，并且已选中第一个用户已经是“自由”。我很卡，为什么我得到这个错误/崩溃，不知道我该怎么解决呢！

谢谢！

Answer 1:

一个block捕捉，包括本身传递的所有变量，但变量myResponseBlock尚未块内初始化。正因为如此，你在呼唤checkIfFree方法与nil值这反过来又导致应用程序崩溃。

有一两件事可以做，以克服这将是你的声明块作为__block变量。

__block __weak void(^weakResponseBlock)(BOOL);

void(^myResponseBlock)(BOOL);

weakResponseBlock = myResponseBlock = ^void(BOOL finished) {
    ...
    if (weakResponseBlock) {
       [self checkIfFree:weakResponseBlock];
    }
}

此外，请注意，块将保持传递到他们的所有变量。在这种情况下，你是保留块内的自我 ，所以它永远不会只要块执行释放。所以，除非另有要求，始终传递一个弱引用块。

__weak UIViewController *weakSelf = self;

weakResponseBlock = myResponseBlock = ^void(BOOL finished) {
    ...
    if (weakResponseBlock) {
       [weakSelf checkIfFree:weakResponseBlock];
    } 
}