ios-upload file with formdata onsumed web api 代码片段

- (IBAction)uploadAction:(id)sender {
    NSString *urlstring=self.urlTextField.text;
    //NSString *poststr=@"";
    NSData *imgData=UIImageJPEGRepresentation(self.previewImageView.image, 0.9f);
    
    NSString *boundary = @"0xKhTmLbOuNdArY";  
    NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary, nil];
    
    NSURL *url=[NSURL URLWithString:urlstring];
    NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:url];
    [request addValue:contentType forHTTPHeaderField:@"Content-Type"];
 
    [request setHTTPMethod:@"POST"];
    NSMutableData *body = [NSMutableData data];
    NSArray *_params=@[@"submitter",@"username"];
    //add submit formdata
    for (NSString *param in _params) {
        [body appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n", param] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[[NSString stringWithFormat:@"%@\r\n", param] dataUsingEncoding:NSUTF8StringEncoding]];
    }
    
    
    
    [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[@"Content-Disposition: form-data; name=\"userfile\"; filename=\"iphonefile.jpg\"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[@"Content-Type: application/octet-stream\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    //[body appendData:[@"submitter: fromiphone" dataUsingEncoding:NSUTF8StringEncoding]];
    
    [body appendData:[NSData dataWithData:imgData]];
    [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    
    [request setHTTPBody:body];
    NSOperationQueue *queue=[[NSOperationQueue alloc] init];
    [NSURLConnection sendAsynchronousRequest:request queue:queue
                           completionHandler:^(NSURLResponse *respone,
                                               NSData *data,
                                               NSError *error)
     {
         if ([data length]>0 && error==nil) {
             NSString *jsonstring=[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
             //[self.respondTextView setText:jsonstring];
             NSLog(@"data:%@",jsonstring);
             //[self performSelectorOnMainThread:@selector(setRespondtext:)withObject:jsonstring waitUntilDone:YES modes:nil];
             //[self performSelectorOnMainThread:@selector(setRespondtext:) withObject:data waitUntilDone:NO];
         }  
     }
     ];