Parse URL parameter String from Dictionary

gistfile1.m

// create parameter string from parameter dictionary
__block NSMutableString *parameterString;
[parameters enumerateKeysAndObjectsUsingBlock:^(id key, id value, BOOL *stop) {
  if (!parameterString) parameterString = [NSMutableString stringWithString:@"?"];
  else [parameterString appendString:@"&"];
        
  // escape value string
  NSString *escapedString = (__bridge NSString*)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)[parameters valueForKey:key], NULL, CFSTR(":/?#[]@!$&’()*+,;="), kCFStringEncodingUTF8);
        [parameterString appendFormat:@"%@=%@", key, escapedString];
}];