ios - 使用 Objective C 创建 JSON 数据并将其发送到服务器

Question

我尝试使用 POST 方法将 JSON 数据发送到服务器端，但我的代码给出了 null JSON 值。我正在使用 Objective C 从 textField 获取数据并将其转换为字符串，但之后将此值转换为 JSON 对象时，它给出 null 值。不知道该怎么办。

这是我的代码:

- (IBAction)loginAction:(UIButton *)sender
{
NSString *post = [NSString stringWithFormat:@"Username=%@&Password=%@" ,self.userNameField.text,self.passwordField.text];
NSData *postData = [post dataUsingEncoding:NSUTF8StringEncoding];
postData = [postData subdataWithRange:NSMakeRange(0, [postData length] - 1)];
NSData*jsonData = [NSJSONSerialization JSONObjectWithData:postData options:NSJSONReadingMutableContainers error:nil];
NSString *postLength = [NSString stringWithFormat:@"%d",[postData length]];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc]init];
[request setURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://172.31.144.227:8080/Analytics/rest/login/post"]]];
[request setHTTPMethod:@"POST"];
[request setValue:postLength forHTTPHeaderField:@"Content-Length" ];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Current-Type"];
[request setHTTPBody:jsonData];
NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[theConnection start];

NSError *error = [[NSError alloc] init];
NSHTTPURLResponse *response = nil;
[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
}

Answer 1

-(void)MessagePost{
NSString * post =[NSString stringWithFormat:@"http://url.com/clients/project_id=%@&user_id=58&question=%@&send_enquiry=Send",[[self.recordchat objectForKey:@"id"] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding],[[_txtfield text] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
NSLog(@"%@",post);
NSData *postdata= [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *postLength=[NSString stringWithFormat:@"%lu",(unsigned long)[postdata length]];
NSMutableURLRequest *request= [[NSMutableURLRequest alloc]init];
[request setURL:[NSURL URLWithString:post]];
[request setHTTPMethod:@"POST"];
[request setValue:postLength forHTTPHeaderField:@"Content-Length"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[request setHTTPBody:postdata];
NSError *error;
NSURLResponse *response;
postdata=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSString *returnstring=[[NSString alloc]initWithData:postdata encoding:NSUTF8StringEncoding];
NSLog(@"String : %@",returnstring);
if (postdata){
    NSDictionary *dict= [NSJSONSerialization JSONObjectWithData:postdata options:NSJSONReadingMutableContainers error:nil];
    NSDictionary* latestLoans = [dict objectForKey:@"status"];
    NSLog(@"Status dict = %@",latestLoans);
}  else{ NSLog(@"Error while posting messages.");}}