Question

I am sending a file to the server. Like in this tutorial: http://zcentric.com/2008/08/29/post-a-uiimage-to-the-web/#comment-8145

- (IBAction)uploadImage {
/*
 turning the image into a NSData object
 getting the image back out of the UIImageView
 setting the quality to 90
*/
NSData *imageData = UIImageJPEGRepresentation(image.image, 90);
// setting up the URL to post to
NSString *urlString = @"http://iphone.zcentric.com/test-upload.php";

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

/*
 add some header info now
 we always need a boundary when we post a file
 also we need to set the content type

 You might want to generate a random boundary.. this is just the same 
 as my output from wireshark on a valid html post
*/
NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"];
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
[request addValue:contentType forHTTPHeaderField: @"Content-Type"];

/*
 now lets create the body of the post
*/
NSMutableData *body = [NSMutableData data];
[body appendData:[[NSString stringWithFormat:@"rn--%@rn",boundary] dataUsingEncoding:NSUTF8StringEncoding]];    
[body appendData:[[NSString stringWithString:@"Content-Disposition: form-data; name="userfile"; filename="ipodfile.jpg"rn"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithString:@"Content-Type: application/octet-streamrnrn"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[NSData dataWithData:imageData]];
[body appendData:[[NSString stringWithFormat:@"rn--%@--rn",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
// setting the body of the post to the reqeust
[request setHTTPBody:body];

// now lets 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);
}

And from the server side:

$uploaddir = './uploads/';
$file = basename($_FILES['userfile']['name']);
$uploadfile = $uploaddir . $file;
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
    echo "http://iphone.zcentric.com/uploads/{$file}";
}

Anyone could please answer me:

• Any way to check if the file was uploaded completely or there is an error and send the result of the process from the server to the app.
• In case there is an interruption (like pressing the home button or a phone call or the network has fallen) will the app finish the uploading when the app is active again.

Basically I have to update a database when the file is uploaded but I have to be sure there were no errors.

Answer 1

As long as your server responds with URL of uploaded file (which means it was uploaded successfully), you can check returnString for being non-empty and containing meaningful URL and returned codes & errors.

NSHTTPURLResponse* response;
NSError* err;
NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&err];
NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
if (err) {
    //Network error happened (DOESN'T mean HTTP error code)
    NSLog(@"Error: %@", err);
    return;
}
if ([response statusCode] != 200) { 
    //Server returned HTTP error code
    NSLog(@"Error: Server returned non 200 code");
    return;
}
if (![NSURL urlWithString:returnString]) { 
    //URL is not valid
    NSLog(@"File URL returned from server is not valid");
    return;
}
//File uploaded
NSLog(@"File uploaded successfully");

This examples assumes you’re using ARC in your project (so no releases).

To correctly handle application suspending, take a look at background tasks. You can make background task from your file upload code and it should continue uploading if application is moved to background.