Here’s how to find a substring in Swift 4.
import Foundation // find substring var s = "bird mouse fish" let strToFind = "mouse" var ns = s as NSString // case sensitive find if (ns.contains(strToFind)) { print("substring found") } // case insensitive find let range = ns.range(of: strToFind, options: .caseInsensitive) if range.location != NSNotFound { // replace s = ns.replacingCharacters(in: range, with: "cat") print(s) // it prints "bird cat fish" }
We simply convert our String to an NSString so we can use the contains function or the range(of: options:) function.
To replace the substring, we again use a NSString method: replacing Characters(in: with:).