ios - 在两个类之间使用 NSDictionary 值

Question

我正在尝试获取两个类之间的 NSDictionary 中的值..

我在Database.m (NSObject类)

中使用此方法

+(void)fetchAllUserWithReference:(NSDictionary *)dictionary {

    FIRDatabaseReference *userReference = [[[FIRDatabase database] reference] child:RTDUSER];
    [userReference observeEventType:FIRDataEventTypeChildAdded withBlock:^(FIRDataSnapshot * _Nonnull snapshot) {
        __block NSDictionary *dict = dictionary;
        dict = snapshot.value;

    } withCancelBlock:nil];
}

我想在 Dashboard.m (UIView Controller) 类中获取 NSDictionary 数据，如下所示..

-(void)retrieveUsers {
    NSDictionary *dict = [[NSDictionary alloc] init];
    [Database fetchAllUserWithReference:dict];    
    NSLog(@"DICT %@",dict);
}

为什么我的Dashboard.m类的NSDictionary总是NULL？我哪里错了？

Answer 1

您可以使用完成处理程序在执行 block 后取回值。

-(void)fetchAllUserWithReference:(NSDictionary *)param
       withCompletionHandler:(void (^)(NSDictionary *response))block{

       FIRDatabaseReference *userReference = [[[FIRDatabase database] reference] child:RTDUSER];
      [userReference observeEventType:FIRDataEventTypeChildAdded withBlock:^(FIRDataSnapshot * _Nonnull snapshot) {
       NSDictionary *dict = snapshot.value;
       block(dict);
    } withCancelBlock:
   block(nil);];
}

-(void)retrieveUsers {
    NSDictionary *dict = [NSDictionary init];
    [self fetchAllUserWithReference:dict withCompletionHandler:^(NSDictionary *response) {
        NSLog(@"%@",response);
    }];
}