Replace occurrences of space in URL

I have a URL in an iPhone application to work with. But the problem is that it has some spaces in the URL. I want to replace the spaces with '%20'. I know that there are the stringByReplacingOccurencesOfString and stringByAddingPercentEscapesUsingEncoding methods. I also have used them. But they are not working for me. The spaces are replaced by some unusual values.

I'm applying those methods on an instance of NSString.

The correct format for replacing space from url is :

Swift 4.2 , Swift 5

var urlString = originalString.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)

Swift 4

var urlString = originalString.addingPercentEncoding(withAllowedCharacters: CharacterSet.urlQueryAllowed)

Objective C

NSString *urlString;//your url string.

urlString = [originalUrl stringByReplacingOccurrencesOfString:@" " withString:@"%20"];

or

urlString = [originalUrl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

iOS 9 and later

urlString = [originalUrl stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

Swift 2.0

let originalUrl = "http://myurl.com/my photo.png"
let urlNew:String = urlReq.stringByAddingPercentEncodingWithAllowedCharacters( NSCharacterSet.URLQueryAllowedCharacterSet())! 

Output:

http://myurl.com/my%20photo.png

To replace occurence in SWIFT 3 :

let updatedUrl = originalUrl.addingPercentEncoding(withAllowedCharacters: NSCharacterSet.urlQueryAllowed)