Question

我创建了一个返回BOOL的新方法，如下所示。

+(BOOL)checkIfGameAlreadyExistsAgainst:(PFUser *)opponentUser {
    // Find all the games where the current user is user1 and the opponentUser is user2
    PFQuery *currentUserIsUser1 = [PFQuery queryWithClassName:@"Game"];
    [currentUserIsUser1 whereKey:kMESGameUser1 equalTo:[PFUser currentUser]];
    [currentUserIsUser1 whereKey:kMESGameUser2 equalTo:opponentUser];
    [currentUserIsUser1 whereKey:kMESGameIsActive equalTo:[NSNumber numberWithBool:YES]];
    [currentUserIsUser1 findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
        if (objects) {
            // We have games where the current user is user1
            // NEED TO RETURN NO TO THIS METHOD AND NOT RUN FURTHER IN METHOD...
            NSLog(@"Results returned for existing game where current user is User1. Results: %@",objects);
        } else {
            // If there are no objects from first query and no error we run the second query
            if (!error) {
                // Find all the games where the current user is user2 and the opponentUser is user1
                PFQuery *currentUserIsUser2 = [PFQuery queryWithClassName:@"Game"];
                [currentUserIsUser2 whereKey:kMESGameUser1 equalTo:opponentUser];
                [currentUserIsUser2 whereKey:kMESGameUser2 equalTo:[PFUser currentUser]];
                [currentUserIsUser2 whereKey:kMESGameIsActive equalTo:[NSNumber numberWithBool:YES]];
                [currentUserIsUser2 findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
                    if (objects) {
                        // We have games where the current user is user2
                        // NEED TO RETURN NO TO THIS METHOD AND NOT RUN FURTHER IN METHOD...
                        NSLog(@"Results returned for existing game where current user is User2. Results: %@",objects);
                    }
                }];
            }
        }
    }];


    return NO;
}

我遇到的问题是如何在方法中的块内返回YES值。请参阅方法中的部分说//不需要返回此方法而不是在方法中进一步运行... 我怎么能在这里回答YES。如果我添加返回YES，则会出现不兼容的指针类型错误。

此外，一旦我将方法返回YES，我该如何调用此方法并根据结果执行某些操作。例如，我需要调用此方法，如果它是真的，那么做一些其他事情，如果不做任何事情......

Answer 1

我不确定你在问什么，所以这里有一个猜测：你希望你的块返回一个值checkIfGameAlreadyExistsAgainst。

当构造一个块时，它通常会生成从其环境引用的任何值的副本。如果您希望块在其环境中修改变量，则必须使用__block标记该变量。在您的代码中，这看起来像：

__block BOOL blockStatus = YES;
[currentUserIsUser1 findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
 {
    ...
    blockStatus = NO;
 }
];

if (!blockStatus)
{
   ...
}

重要提示：您正在呼叫的方法的名称findObjectsInBackgroundWithBlock表示该块可能未被同步调用，这意味着该呼叫可能会返回在块执行之前。如果是这种情况，您需要以不同的方式解决问题;这可能涉及调用同步等效的findObjectsInBackgroundWithBlock或修改checkIfGameAlreadyExistsAgainst，以便它接受一个与其结果异步调用的块，而不是直接返回一个值。

HTH

BOOL方法不在块内返回YES

1 个答案: