Multipart POST to upload jpeg sample code for iOS

imgge_uploader.m

@interface ImageUploader : NSObject {
    NSData *theImage;
}
@property (retain) NSData *theImage;
- (void) syncUpload:(NSData *) uploadImage;
@end


#import "ImageUploader.h"

#define NOTIFY_AND_LEAVE(X) {[self cleanup:X]; return;}
#define DATA(X)	[X dataUsingEncoding:NSUTF8StringEncoding]

// Posting constants
#define IMAGE_CONTENT @"Content-Disposition: form-data; name=\"%@\"; filename=\"image.jpg\"\r\nContent-Type: image/jpeg\r\n\r\n"
#define BOUNDARY @"------------0x0x0x0x0x0x0x0x"

@implementation ImageUploader
@synthesize theImage;


- (void) syncUpload:(NSData *) uploadImage
{
    self.theImage = uploadImage;
    [self main];
}

- (void) cleanup: (NSString *) output
{
	self.theImage = nil;
//    NSLog(@"******** %@", output);
}

- (NSData*)generateFormDataFromPostDictionary:(NSDictionary*)dict
{
    id boundary = BOUNDARY;
    NSArray* keys = [dict allKeys];
    NSMutableData* result = [NSMutableData data];
	
    for (int i = 0; i < [keys count]; i++) 
    {
        id value = [dict valueForKey: [keys objectAtIndex:i]];
        [result appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
		
		if ([value isKindOfClass:[NSData class]]) 
		{
			// handle image data
			NSString *formstring = [NSString stringWithFormat:IMAGE_CONTENT, [keys objectAtIndex:i]];
			[result appendData: DATA(formstring)];
			[result appendData:value];
		}
		
		NSString *formstring = @"\r\n";
        [result appendData:DATA(formstring)];
    }
	
	NSString *formstring =[NSString stringWithFormat:@"--%@--\r\n", boundary];
    [result appendData:DATA(formstring)];
    return result;
}


// NSOperationQueueによる非同期化を見据えてmainにしています。
- (void) main
{
	if (!self.theImage) {
		NOTIFY_AND_LEAVE(@"Please set image before uploading.");
    }
    NSString* MultiPartContentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", BOUNDARY];
    
	NSMutableDictionary* post_dict = [[NSMutableDictionary alloc] init];
	[post_dict setObject:@"testimage" forKey:@"filename"];
    [post_dict setObject:self.theImage forKey:@"data[User][image]"];
	
	NSData *postData = [self generateFormDataFromPostDictionary:post_dict];
	[post_dict release];
	
    NSString *baseurl = @"https://example.com/api/upload_image";
    NSURL *url = [NSURL URLWithString:baseurl];
    NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url];
    if (!urlRequest) NOTIFY_AND_LEAVE(@"Error creating the URL Request");
	
    [urlRequest setHTTPMethod: @"POST"];
  	[urlRequest setValue:MultiPartContentType forHTTPHeaderField: @"Content-Type"];
    [urlRequest setHTTPBody:postData];
	
    NSError *error;
    NSURLResponse *response;
	NSData* result = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error];
    //NSLog(@"***** result =%@", result);
    
    if (!result)
	{
		[self cleanup:[NSString stringWithFormat:@"upload error: %@", [error localizedDescription]]];
		return;
	}
	
	// Return results
    NSString *outstring = [[[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding] autorelease];
    NSLog(@"***** outstring =%@", outstring);
	[self cleanup: outstring];
}

@end