字符串的颜色部分

Question

试图在Swift5中使用下面的代码来给字符串的一部分上色，问题是该字符串是一个变量，尚不存在，因此为什么该代码不起作用。

该代码使用存在的字符串进行工作：

let main_string = "Headline 5"
let string_to_color = "5"

但是，这不起作用：

let main_string = "Headline "
let string_to_color = "\(stringTime) min" //stringTime is a string of a number, for example "21"


let range = (main_string as NSString).range(of: string_to_color)

let attribute = NSMutableAttributedString.init(string: main_string)
attribute.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.red , range: range)

 self.Label.attributedText = attribute

任何想法，我如何使它变色为一个可变的字符串并将其添加到我的字符串中？

Answer 1

对于此示例，我有一个计时器，它每秒触发一次，然后用显示的字符串中间的递增计数器变量构建一个字符串-这符合您的要求吗？

class ViewController: UIViewController {

@IBOutlet weak var lblDisplay: UILabel!
var timer : Timer!
var timerLoop : Int = 0


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerFired), userInfo: nil, repeats: true)
}

@objc func timerFired()
{
    timerLoop += 1

    let main_string = "First part \(timerLoop) second part"
    let string_to_color = "\(timerLoop)" //stringTime is a string of a number, for example "21"


    let range = (main_string as NSString).range(of: string_to_color)

    let attribute = NSMutableAttributedString.init(string: main_string)
    attribute.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.red , range: range)

     self.lblDisplay.attributedText = attribute
}

}