Find String from String using NSRegularExpression Swift - swift

Question

I want to fetch url of images from the String using NSRegularExpression.
func findURlUsingExpression(urlString: String){
do{
let expression = try NSRegularExpression(pattern: "\\b(http|https)\\S*(jpg|png)\\b", options: NSRegularExpressionOptions.CaseInsensitive)
let arrMatches = expression.matchesInString(urlString, options: NSMatchingOptions(rawValue: 0), range: NSMakeRange(0, urlString.characters.count))
for match in arrMatches{
let matchText = urlString.substringWithRange(Range(urlString.startIndex.advancedBy(match.range.location) ..< urlString.startIndex.advancedBy(match.range.location + match.range.length)))
print(matchText)
}
}catch let error as NSError{
print(error.localizedDescription)
}
}
It works with just the simple string but not with the HTML String.
Working Example:
let tempString = "jhgsfjhgsfhjgajshfgjahksfgjhs http://jhsgdfjhjhggajhdgsf.jpg jahsfgh asdf ajsdghf http://jhsgdfjhjhggajhdgsf.png"
findURlUsingExpression(tempString)
Output:
http://jhsgdfjhjhggajhdgsf.jpg
http://jhsgdfjhjhggajhdgsf.png
But not working with this one: http://www.writeurl.com/text/478sqami3ukuug0r0bdb/i3r86zlza211xpwkdf2m

Answer 1

Don't roll your own regex if you can help it. Easiest and safest way is to use NSDataDetector. By using NSDataDetector you leverage a pre-built, heavily used parsing tool which should already have most of the bugs shaken out of it.
Here is a good article on it: NSData​Detector
NSDataDetector is a subclass of NSRegularExpression, but instead of
matching on an ICU pattern, it detects semi-structured information:
dates, addresses, links, phone numbers and transit information.
import Foundation
let tempString = "jhgsfjhgsfhjgajshfgjahksfgjhs http://example.com/jhsgdfjhjhggajhdgsf.jpg jahsfgh asdf ajsdghf http://example.com/jhsgdfjhjhggajhdgsf.png"
let types: NSTextCheckingType = [.Link]
let detector = try? NSDataDetector(types: types.rawValue)
detector?.enumerateMatchesInString(tempString, options: [], range: NSMakeRange(0, (tempString as NSString).length)) { (result, flags, _) in
if let result = result?.URL {
print(result)
}
}
// => "http://example.com/jhsgdfjhjhggajhdgsf.jpg"
// => "http://example.com/jhsgdfjhjhggajhdgsf.png"
The example is from that site, adapted to search for a link.