Selecting the text just updated with replaceRange(

问题:

I'm changing the content of a UITextView with the following code:

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

Then I would like to select the new text. I'm trying to use the following code:

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!)
 }

The problem is that I don't know how to get the startingPoint and endingPoint values. Is it possible to get them in some ways from the replaceRange(range: UITextRange, withText: String) statement?

EDIT: To try to clarify a bit my question:

// 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"

How to select the new text ("happy")?

回答1:

You just need to use the length of the string to determine the UITextRange of the selection. For example:

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()


           }
}

In the above example "the" will be replaced by "how now brown cow" and "how now brown cow" will be selected. I'm using a convenience function to convert an NSRange into a UITextRange. The range will start at index 0 and go for 3 characters ("the"). I replace that with the string "how now brown cow." Then I use the previous UITextRange and my replacement string to construct a new UITextRange (textView.textRangeFromPosition(range.start, toPosition: textView.positionFromPosition(range.start, offset: text.characters.count)!)). I then set to the textView's selectedTextRange. You should make sure that your UITextView is selectable and then call becomeFirstResponder on yourUITextView`.