将JSON数据POST到现有对象中

Question

我正在从格式如下的URL中检索JSON数据:

{"zoneresponse":
{"tasks":
 [{"datafield1":"datafor1", 
   "datafield2":"datafor2", 
   "datafield3":"datafor3",...
 }]
}}

我无法控制结构,因为它来自私有API.

如何在现有对象的选定数据字段中插入数据？

我试过这个:

self.responseData = [NSMutableData data];

//testingURL is the api address to the specific object in tasks
NSURL *url = [NSURL URLWithString:testingURL];

NSMutableDictionary *params = [[NSMutableDictionary alloc] init];
[[[params objectForKey:@"zoneresponse"] objectForKey:@"tasks"] setValue:@"HelloWorld" forKey:@"datafield1"];
//HAVE TRIED setObject: @"" objectForKey: @"" as well

//*****PARAMS IS EMPTY WHEN PRINTED IN NSLog WHICH IS PART OF THE ISSUE - SETTING VALUE DOES NOT WORK

NSError * error = nil;

NSLog(@"Params is %@", params);

NSData *requestdata = [NSJSONSerialization dataWithJSONObject:params options:0 error:&error];

NSMutableURLRequest *request;
request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];
[request setValue:[NSString stringWithFormat:@"%d", [requestdata length]] forHTTPHeaderField:@"Content-Length"];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[request setHTTPBody:requestdata];

NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];


if(conn) {
    NSLog(@"Connection Successful, connection is: %@", conn);

} else {
    NSLog(@"Connection could not be made");
}

正在建立连接,但字典参数在打印时为空(setValue未显示),并且未在我选择的字段中输入任何数据.

我已经检查了这些链接,但没有解释它是否会插入到正确的字段中并暗示它将创建一个新对象而不是更新现有对象.

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委托方法

//any time a piece of data is received we will append it to the responseData object
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.responseData appendData:data];

    NSError *jsonError;

    id responseDict =
    [NSJSONSerialization JSONObjectWithData:self.responseData
                                options:NSJSONReadingAllowFragments
                                  error:&jsonError];

    NSLog(@"Did Receive data %@", responseDict);
}

 //if there is some sort of error, you can print the error or put in some other handling here, possibly even try again but you will risk an infinite loop then unless you impose some sort of limit
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    // Clear the activeDownload property to allow later attempts
    self.responseData = nil;

    NSLog(@"Did NOT receive data ");

}

//connection has finished, the requestData object should contain the entirety of the response at this point
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSError *jsonError;
    id responseDict =
    [NSJSONSerialization JSONObjectWithData:self.responseData
                                options:NSJSONReadingAllowFragments
                                  error:&jsonError];
    if(responseDict)
    {
        NSLog(@"%@", responseDict);
    }
    else
    {
        NSLog(@"%@", [jsonError description]);
    }

    //clear out our response buffer for future requests
    self.responseData = nil;
}

这里的第一个方法声明数据是通过"Did Receive data(null)"接收的,连接没有错误,但是最终方法打印错误消息"JSON文本没有以数组或对象开始,并且选项允许片段未设置.",这是可以理解的,因为没有数据或对象被发送.

如何将数据插入现有对象的选定字段？

Answer 1

你做错了:

NSMutableDictionary *params = [[NSMutableDictionary alloc] init];
[[[params objectForKey:@"zoneresponse"] objectForKey:@"tasks"] setValue:@"HelloWorld" forKey:@"datafield1"];

你params是空字典,不会返回任何对象[params objectForKey:@"zoneresponse"].

试试这个:

NSMutableDictionary *params = [NSMutableDictionary new];
params[@"zoneresponse"] = @{@"tasks": @{@"datafield1": @"HelloWorld"}};

这将工作,但密钥的对象@"tasks"将是不可变的.要将另一个对象添加到tasks字典中,我们需要使其变为可变:

NSMutableDictionary *params = [NSMutableDictionary new];
NSMutableDictionary *tasks = [NSMutableDictionary new];
params[@"zoneresponse"] = @{@"tasks": tasks};
params[@"zoneresponse"][@"tasks"][@"datafield1"] = @"HelloWorld";

要么

NSMutableDictionary *params = [NSMutableDictionary new];    
params[@"zoneresponse"] = @{@"tasks": [@{@"datafield1": @"HelloWorld"} mutableCopy]};

然后你可以添加另一个对象tasks:

params[@"zoneresponse"][@"tasks"][@"datafield2"] = @"HelloWorld2";
params[@"zoneresponse"][@"tasks"][@"datafield3"] = @"HelloWorld3";

我想我的回答会为你的字典操作带来一些清晰度.