[Swift] 문자열 중에 특정 문구가 어느 위치에 위치하는 지 알아내는 코드

import Foundation
 
// Input string.
let line = "a soft orange cat"
 
// Search for one string in another.
var result = line.rangeOfString("orange",
    options: NSStringCompareOptions.LiteralSearch,
    range: line.startIndex..<line.endIndex,
    locale: nil)
 
// See if string was found.
if let range = result {
 
    // Display range.
    print(range)
 
    // Start of range of found string.
    var start = range.startIndex
 
    // Display string starting at first index.
    print(line[start..<line.endIndex])
 
    // Display string before first index.
    var beforeStart = start.predecessor()
    print(line[line.startIndex..<beforeStart])
}