NSData and Uploading Images via POST in iOS

Question

I have been combing through the many many posts about uploading images via POST in iOS. Despite the wealth of information on this topic, I cannot manage to correctly upload JPEG data taken from my iPhone Simulator Photo Library. The data, once on the server, is just a huge string of hexidecimal. Shouldn't NSData just be a byte stream? I don't get whats going on with all the hex, or why this code seems to work for everyone else.

Here is the code in question:

-(void)uploadWithUserLocationString:(NSString*)userLocation{
NSString *urlString = @"http://some.url.com/post";

// set up the form keys and values (revise using 1 NSDictionary at some point - neater than 2 arrays)
NSArray *keys = [[NSArray alloc] initWithObjects:@"auth",@"text",@"location",nil];
NSArray *vals = [[NSArray alloc] initWithObjects:self.authToken,self.textBox.text,userLocation,nil];

// set up the request object
NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease];
[request setURL:[NSURL URLWithString:urlString]];
[request setHTTPMethod:@"POST"];

//Add content-type to Header. Need to use a string boundary for data uploading.
NSString *boundary = [NSString stringWithString:@"0xKhTmLbOuNdArY"];
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
[request addValue:contentType forHTTPHeaderField: @"Content-Type"];

//create the post body
NSMutableData *body = [NSMutableData data];
[body appendData:[[NSString stringWithFormat:@"--%@\r\n",boundary] dataUsingEncoding:NSASCIIStringEncoding]];

//add (key,value) pairs (no idea why all the \r's and \n's are necessary ... but everyone seems to have them)
for (int i=0; i<[keys count]; i++) {
    [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n",[keys objectAtIndex:i]] dataUsingEncoding:NSASCIIStringEncoding]];
    [body appendData:[[NSString stringWithFormat:@"%@",[vals objectAtIndex:i]] dataUsingEncoding:NSASCIIStringEncoding]];
    [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSASCIIStringEncoding]];
}
[body appendData:[[NSString stringWithString:@"Content-Disposition: form-data; name=\"image\"\r\n"] dataUsingEncoding:NSASCIIStringEncoding]];
[body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSASCIIStringEncoding]];
[body appendData:[NSData dataWithData:self.imageData]];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSASCIIStringEncoding]];

// set the body of the post to the reqeust
[request setHTTPBody:body];

// make the connection to the web
NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];

NSLog(returnString);
[keys release];
[vals release];
}

Thanks for your time.

Answer 1

This code works in my app. If you're not using ARC you'll need to modify the code to release anything alloc'ed.

// create request
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];                                    
[request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
[request setHTTPShouldHandleCookies:NO];
[request setTimeoutInterval:30];
[request setHTTPMethod:@"POST"];

// set Content-Type in HTTP header
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
[request setValue:contentType forHTTPHeaderField: @"Content-Type"];

// post body
NSMutableData *body = [NSMutableData data];

// add params (all params are strings)
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", [_params objectForKey:param]] dataUsingEncoding:NSUTF8StringEncoding]];
}

// add image data
NSData *imageData = UIImageJPEGRepresentation(imageToPost, 1.0);
if (imageData) {
    [body appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"image.jpg\"\r\n", FileParamConstant] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithString:@"Content-Type: image/jpeg\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:imageData];
    [body appendData:[[NSString stringWithFormat:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}

[body appendData:[[NSString stringWithFormat:@"--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];

// setting the body of the post to the reqeust
[request setHTTPBody:body];

// set URL
[request setURL:requestURL];

Answer 2

i hope this code will help some body else ...

//create request
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];

//Set Params
[request setHTTPShouldHandleCookies:NO];
[request setTimeoutInterval:60];
[request setHTTPMethod:@"POST"];

//Create boundary, it can be anything
NSString *boundary = @"------VohpleBoundary4QuqLuM1cE5lMwCy";

// set Content-Type in HTTP header
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
[request setValue:contentType forHTTPHeaderField: @"Content-Type"];

// post body
NSMutableData *body = [NSMutableData data];

//Populate a dictionary with all the regular values you would like to send.
NSMutableDictionary *parameters = [[NSMutableDictionary alloc] init];

[parameters setValue:param1 forKey:@"param1-name"];

[parameters setValue:param2 forKey:@"param2-name"];

[parameters setValue:param3 forKey:@"param3-name"];


// add params (all params are strings)
for (NSString *param in parameters) {
    [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", [parameters objectForKey:param]] dataUsingEncoding:NSUTF8StringEncoding]];
}

NSString *FileParamConstant = @"imageParamName";

NSData *imageData = UIImageJPEGRepresentation(imageObject, 1);

//Assuming data is not nil we add this to the multipart form
if (imageData)
{
    [body appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"image.jpg\"\r\n", FileParamConstant] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[@"Content-Type:image/jpeg\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:imageData];
    [body appendData:[[NSString stringWithFormat:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}

//Close off the request with the boundary
[body appendData:[[NSString stringWithFormat:@"--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];

// setting the body of the post to the request
[request setHTTPBody:body];

// set URL
[request setURL:[NSURL URLWithString:baseUrl]];

[NSURLConnection sendAsynchronousRequest:request
                                   queue:[NSOperationQueue mainQueue]
                       completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

                           NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*)response;

                           if ([httpResponse statusCode] == 200) {

                               NSLog(@"success");
                           }

                       }];

Answer 3

Take a look at Apple's SimpleURLConnections example project. You can use the PostController from there with a few modifications.

However - it's not exactly simple. The difference to the solution above is that Apple's is using a stream to stream the file to the server. That's much more memory-friendly than keeping the encoded image data around for the duration of the upload. It's also way more complicated.

Answer 4

NSData *imgData = UIImagePNGRepresentation(imgUser.image);

NSString *str=[NSString stringWithFormat:@"%@upload_image",appDelegate.strRoot];
NSString *urlString = [NSString stringWithFormat:@"%@",str];

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:[NSURL URLWithString:urlString]];
[request setHTTPMethod:@"POST"];
NSMutableData *body = [NSMutableData data];
NSString *boundary = @"---------------------------14737809831466499882746641449";
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
[request addValue:contentType forHTTPHeaderField: @"Content-Type"];

[body appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"Content-Disposition: form-data; name=\"file\"; filename=\"a.jpg\"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"Content-Type: application/octet-stream\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[NSData dataWithData:imgData]];
[body appendData:[@"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];

//  parameter UserId

[body appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userid\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];

[body appendData:[appDelegate.strUserID dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];


// close form
[body appendData:[[NSString stringWithFormat:@"--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];


// setting the body of the post to the request 
[request setHTTPBody:body];


NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
// NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
NSDictionary *dict=[NSJSONSerialization JSONObjectWithData:returnData options:NSJSONReadingMutableLeaves error:nil];
NSLog(@"%@",dict);

Answer 5

I see that you send multiple files in one request, correct?

From HTTP specification, you should use multipart/mixed Content-type inside embedding multipart/form-data

Example from link above:

Content-type: multipart/form-data, boundary=AaB03x

--AaB03x
content-disposition: form-data; name="field1"

 Joe Blow
 --AaB03x
 content-disposition: form-data; name="pics"
 Content-type: multipart/mixed, boundary=BbC04y

 --BbC04y
  Content-disposition: attachment; filename="file1.txt"