ios - 返回数组时不兼容的 block 指针类型？

Question

我在 parse.com 上有一个食物对象数据库，我试图返回一个包含所有食物的数组。

- (NSArray*) allFoods {

    NSMutableArray *foodArr = [NSMutableArray array];
    PFQuery * foodQuery = [PFQuery queryWithClassName:@"Food"];
    foodQuery.limit = 5000;
    [foodQuery findObjectsInBackgroundWithBlock:^(NSArray * foods, NSError * error) {
            for (PFObject *foodRaw in foods) {
                MenuItem *food = [[MenuItem alloc] initWithName:[foodRaw valueForKey:@"name"]  andURL:nil];
                [foodArr addObject:food];
            }

        return foodArr;

    }];
}

但是，该 block 需要 void，我无法在不导致错误的情况下包含 return 语句。

不兼容的 block 指针类型将“NSMutableArray *(^)(NSArray *__strong, NSError *__strong)”发送到“PFArrayResultBlock”类型的参数(又名“void (^)(NSArray *__strong, NSError *__strong)” ')

Answer 1

你应该使用类似的东西:

typedef void (^ArrayResponseBlock)(NSArray *array);

- (void) allFoodsAsyncWithCompletion:(ArrayResponseBlock)completionBlock {

    NSMutableArray *foodArr = [NSMutableArray array];
    PFQuery * foodQuery = [PFQuery queryWithClassName:@"Food"];
    foodQuery.limit = 5000;
    [foodQuery findObjectsInBackgroundWithBlock:^(NSArray * foods, NSError * error) {
        for (PFObject *foodRaw in foods) {
            MenuItem *food = [[MenuItem alloc] initWithName:[foodRaw valueForKey:@"name"]  andURL:nil];
            [foodArr addObject:food];
        }

        completionBlock(foodArr);        
    }];
}