Question

我正在使用AFNetworking AFHTTPSessionManager发出GET请求。当我记录响应对象时，将记录responseObject。当我尝试记录我的locationIDsDictionary时，我得到null。范围问题？ locationIDsDictionary是否需要是_block类型？

viewController.h
@property (strong, nonatomic) NSDictionary *locationIDsDictionary;

viewController.m
    [[LPAuthClient sharedClient]GET:getLocationIDString parameters:nil success:^(NSURLSessionDataTask *task, id responseObject) {
        NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)task.response;
        if (httpResponse.statusCode == 200) {
            dispatch_async(dispatch_get_main_queue(), ^{

                _locationArray = responseObject[@"data"];
                NSLog(@"Response %@", responseObject);
            });
        }

    } failure:^(NSURLSessionDataTask *task, NSError *error) {
        NSLog(@"Failure %@", error);
    }];

    NSLog(@"locationIDsDictionary %@", _locationIDsDictionary);

编辑：输出

 Response {
data =     (
            {
        id = 45388148;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = "TESTING HATE VENUE";
    },
            {
        id = 208947000;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = "The Greatest Isreal";
    },
            {
        id = 86128772;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = "Pike street";
    },
            {
        id = 33208867;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = abcde;
    },
            {
        id = 104267842;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = "somewhere over south dakota";
    },
            {
        id = 232446516;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = wow;
    },
            {
        id = 107511313;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = "Yum Yum.com";
    },
            {
        id = 189736241;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = "wow;l";
    },
            {
        id = 246109339;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = Fused;
    },
            {
        id = 153279132;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = 333;
    },
            {
        id = 115790356;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = "Bar Karma";
    },
            {
        id = 50341151;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = popoopo;
    },
            {
        id = 121590347;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = 26;
    },
            {
        id = 75286586;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = wow;
    },
            {
        id = 72889805;
        latitude = "37.785834";
        longitude = "-122.406417";
        name = test;
    },
            {
        id = 284599098;
        latitude = "37.785834009";
        longitude = "-122.406416997";
        name = "Urban Safari";
    },
            {
        id = 89500038;
        latitude = "37.785835266";
        longitude = "-122.406417847";
        name = "Cali Home";
    },
            {
        id = 8736810;
        latitude = "37.785835266";
        longitude = "-122.406417847";
        name = "Test%20Test%20Test";
    },
            {
        id = 45031994;
        latitude = "37.78584";
        longitude = "-122.4064";
        name = japaneses;
    },
            {
        id = 35874897;
        latitude = "37.785806574";
        longitude = "-122.406477728";
        name = "Hotel Palomar Fifth Floor Restaurant";
    }
);
meta =     {
    code = 200;
};

}

Answer 1

你写......

当我尝试记录locationIDsDictionary时，我得到null。

由于你没有共享这个日志，我假设你正在做这样的事情......

[self runMyGetLocationMethodAsynchronously];
NSLog(@"%@", _locationIDsDictionary);

这不起作用，因为您在异步方法的成功块中设置了_locationIDsDictionary。在该块运行之前，不会设置您的字典。

Answer 2

以CrimsonChris＆＃39;为基础回答，GET: parameters: success:方法是异步的。在这段代码中：

[[LPAuthClient sharedClient] GET:getLocationIDString parameters:nil success:^(NSURLSessionDataTask *task, id responseObject) {
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)task.response;
    if (httpResponse.statusCode == 200) {
        dispatch_async(dispatch_get_main_queue(), ^{
            _locationArray = responseObject[@"data"];
            NSLog(@"Response %@", responseObject);
        });
    }
} failure:^(NSURLSessionDataTask *task, NSError *error) {
    NSLog(@"Failure %@", error);
}];
NSLog(@"locationIDsDictionary %@", _locationIDsDictionary);

success参数是您的完成块，所以：

^(NSURLSessionDataTask *task, id responseObject) {
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)task.response;
    if (httpResponse.statusCode == 200) {
        dispatch_async(dispatch_get_main_queue(), ^{
            _locationArray = responseObject[@"data"];
            NSLog(@"Response %@", responseObject);
        });
    }
} failure:^(NSURLSessionDataTask *task, NSError *error) {
    NSLog(@"Failure %@", error);
}

仅当iOS 完成下载任务时才会调用

，因此只有在下载任务完成时才会分配字典。同时，剩余的代码行正在执行，因此异步的含义 - 在不同的线程上执行。如果它是同步的，那么代码将被停止，直到代码块完成为止，这很糟糕，你会发现它在iOS应用程序中被翻译成了freezy UI。

因此，在执行下载任务时仍然会调用NSLog(@"locationIDsDictionary %@", _locationIDsDictionary);，因此评估为nil - 当然除非您的网速疯狂 :)

块，范围和设置变量目标C.

2 个答案: