快速为所有出现的字符串着色

这段代码

var textSearch="hi"
var textToShow="hi hihi hi" 
var rangeToColor = (textToShow as NSString).rangeOfString(textSearch)
var attributedString = NSMutableAttributedString(string:textToShow)
attributedString.addAttribute(NSForegroundColorAttributeName, value: UIColor.yellowColor() , range: rangeToColor)
TextView.attributedText=attributedString

给我 NSRange 来为 TextView 内的字符串着色。 问题是我只返回第一次出现的情况。 如果单词包含“hi hihi hi”，则仅第一个“hi”被着色。 如何获取字符串的所有出现位置？

Swift 5

let attrStr = NSMutableAttributedString(string: "hi hihi hey")
let inputLength = attrStr.string.count
let searchString = "hi"
let searchLength = searchString.characters.count
var range = NSRange(location: 0, length: attrStr.length)

while (range.location != NSNotFound) {
    range = (attrStr.string as NSString).range(of: searchString, options: [], range: range)
    if (range.location != NSNotFound) {
        attrStr.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.yellow, range: NSRange(location: range.location, length: searchLength))
        range = NSRange(location: range.location + range.length, length: inputLength - (range.location + range.length))
    }
}

Swift 3

let attrStr = NSMutableAttributedString(string: "hi hihi hey")
let inputLength = attrStr.string.characters.count
let searchString = "hi"
let searchLength = searchString.characters.count
var range = NSRange(location: 0, length: attrStr.length)

while (range.location != NSNotFound) {
    range = (attrStr.string as NSString).range(of: searchString, options: [], range: range)
    if (range.location != NSNotFound) {
        attrStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.yellow(), range: NSRange(location: range.location, length: searchLength))
        range = NSRange(location: range.location + range.length, length: inputLength - (range.location + range.length))
    }
}

Swift 2

let attrStr = NSMutableAttributedString(string: "hi hihi hey")
let inputLength = attrStr.string.characters.count
let searchString = "hi"
let searchLength = searchString.characters.count
var range = NSRange(location: 0, length: attrStr.length)

while (range.location != NSNotFound) {
    range = (attrStr.string as NSString).rangeOfString(searchString, options: [], range: range)
    if (range.location != NSNotFound) {
        attrStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.yellowColor(), range: NSRange(location: range.location, length: searchLength))
        range = NSRange(location: range.location + range.length, length: inputLength - (range.location + range.length))
    }
}