选择使用replaceRange更新的文本(范围: UITextRange，withText: String)

Question

我正在用以下代码更改UITextView的内容：

mainTextField.replaceRange((theRange), withText: newStr)

然后我想选择新的文本。我试图使用以下代码：

mainTextField.becomeFirstResponder()

let startPosition = mainTextField.positionFromPosition(mainTextField.beginningOfDocument, inDirection: UITextLayoutDirection.Right, offset: startingPoint)
let endPosition = mainTextField.positionFromPosition(mainTextField.beginningOfDocument, inDirection: UITextLayoutDirection.Right, offset: endingPoint)

 if startPosition != nil && endPosition != nil {
    mainTextField.selectedTextRange = mainTextField.textRangeFromPosition(startPosition!, toPosition: endPosition!)
 }

问题是我不知道如何获得startingPoint和endingPoint值。是否可以从replaceRange(range: UITextRange，withText: String)语句中获得它们？

编辑:试图澄清一点我的问题：

// mainTextField content = "Have a good day"
// mainTextField selected text = "good"

mainTextField.replaceRange((theRange), withText: "happy")
// here theRange refers the selected text "good" not the new one "happy"

如何选择新的文本(“快乐”)？

Answer 1

您只需要使用字符串的长度来确定所选内容的UITextRange。例如：

extension UITextView // I created this become sometimes it's nice to work with NSRange rather than UITextRange but it's not necessary for your problem.
{
    func textRangeFromNSRange(range:NSRange) -> UITextRange?
    {
        let beginning = self.beginningOfDocument
        guard let start = self.positionFromPosition(beginning, offset: range.location), end = self.positionFromPosition(start, offset: range.length) else { return nil}

        return self.textRangeFromPosition(start, toPosition: end)
    }
}

class ViewController: UIViewController {

    @IBOutlet weak var textView: UITextView!

    override func viewDidAppear(animated: Bool) {
            super.viewDidAppear(animated)
            self.textView.selectable = true
            self.textView.text = "the quick brown fox jumped over the lazy dog"
            let range = self.textView.textRangeFromNSRange(NSRange(location: 0, length: 3))!
            let text = "how now brown cow"
            self.textView.replaceRange(range, withText: text)
            self.textView.selectedTextRange = textView.textRangeFromPosition(range.start, toPosition: textView.positionFromPosition(range.start, offset: text.characters.count)!) //should probably break this into multiple lines for better readability
            self.textView.becomeFirstResponder()


           }
}

在上面的例子中，" the“将改为"how now布朗牛”，"how now brown奶牛“将被选中。我使用一个方便的函数将一个NSRange转换为一个UITextRange。范围将从索引0开始，然后转到3个字符(" The ")。我用“现在是棕色牛”来代替它。然后使用前面的UITextRange和替换字符串来构造一个新的UITextRange (textView.textRangeFromPosition(range.start, toPosition: textView.positionFromPosition(range.start, offset: text.characters.count)!))。然后设置为textView的selectedTextRange。您应该确保您的UITextView是可选的，然后调用becomeFirstResponder on yourUITextView` `。