在Swift 3中，如何从包含许多此类字符的字符串中替换URL的单个字符？

Question

So I have an image URL:

https://images.gr-assets.com/books/1410762334m/135625.jpg

And I want to change the letter "m" after the first block of numbers (1410762334) with the letter "l" .

I tried using replacingOccurrences(of: "m", with: "l", options: .literal, range: nil) and as expected, it replaces all m's with l's and it doesn't work. I know it's got to do with the range but I'm not sure what to put as the range. Please enlighten me :)

Thanks in advance!

Answer 1

You should use NSRegularExpression for this.

• Firstly, this code searches for a numeric value followed by the letter m and a slash ( / ).
• After that, it searches for m in only that range and replaces it with an l .

---

let urlString: NSString = "https://images.gr-assets.com/books/1410762334m/135625.jpg"

do {
    let regex = try NSRegularExpression(pattern: "[0-9]m/", options: .caseInsensitive)

    let fullRange = NSMakeRange(0, urlString.length)
    let matchRange = regex.rangeOfFirstMatch(in: urlString as String, options: [], range: fullRange)

    let modString = urlString.replacingOccurrences(of: "m", with: "l", options: .caseInsensitive, range: matchRange)
} catch let error {
    //NSRegularExpression threw an error; handle it properly
    print(error.localizedDescription)
}

Swift 4

let urlString = "https://images.gr-assets.com/books/1410762334m/135625.jpg"

do {
    let regex = try NSRegularExpression(pattern: "[0-9]m/", options: .caseInsensitive)

    let fullRange = NSMakeRange(0, urlString.count)
    let matchRange = regex.rangeOfFirstMatch(in: urlString, options: [], range: fullRange)

    let modString = urlString.replacingOccurrences(of: "m", with: "l", options: .caseInsensitive, range: Range(matchRange, in: urlString))
} catch let error {
    //NSRegularExpression threw an error; handle it properly
    print(error.localizedDescription)
}

Answer 2

For this answer I'm going to assume that the number part before the m is the only dynamic part of the URL.

import Foundation

let url = "https://images.gr-assets.com/books/1410762334m/135625.jpg"

if let range = url.range(of: "^https://images.gr-assets.com/books/[0-9]*", options: .regularExpression) {
  let changedUrl = "\(url[range])l/135625.jpg"
}