NetworkAction.m

-(void)submitPostRequestWithUrl:(NSURL*)url
{
    NSString* boundary = @"---------------------------14737809831466499882746641449";
    
    NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:self.timeOut];

    [request setHTTPMethod:@"POST"];
    [request setValue:[NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary] forHTTPHeaderField:@"Content-Type"];
    
    NSData* postbody = [NSData dataForPOSTWithDictionary:self.postParameters boundary:boundary];
       
    [request setHTTPBody:postbody];

    self.request = request;

    [self submitRequest];
}

NSData+POST.m

+(NSData*)dataForPOSTWithDictionary:(NSDictionary *)dictionary boundary:(NSString *)boundary
{
    NSMutableData* postBodyData = [NSMutableData data];
    
    for(NSString* key in dictionary) 
    {
        id value = [dictionary valueForKey:key];
        
        if([value isKindOfClass:[NSData class]]) 
        {
            [postBodyData appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
            [postBodyData appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"%@.jpg\"\r\n", key, key] dataUsingEncoding:NSUTF8StringEncoding]];
            [postBodyData appendData:[[NSString stringWithFormat:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
            
            [postBodyData appendData:value];
        } 
        else 
        {
            [postBodyData appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
            [postBodyData appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n", key] dataUsingEncoding:NSUTF8StringEncoding]];
            [postBodyData appendData:[[NSString stringWithFormat:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];

            [postBodyData appendData:[[NSString stringWithFormat:@"%@", value] dataUsingEncoding:NSUTF8StringEncoding]];
        }

        [postBodyData appendData:[[NSString stringWithString:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    }
    
    [postBodyData appendData:[[NSString stringWithFormat:@"--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
            
    return postBodyData;
}