how to append % sign after input

extension ViewController: UITextFieldDelegate {
    
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let currentText = textField.text! as NSString
        let newText = currentText.replacingCharacters(in: range, with: string)
        if newText.hasSuffix("%"){
            textField.text = newText
        }else{
            textField.text = "\(newText) %"
            
        }
        return true
    }
}

as in the picture i just want 1 % sign after the numbers.

CodePudding user response：

https://developer.apple.com/documentation/uikit/uitextfielddelegate/1619599-textfield says:

Return Value: true if the specified text range should be replaced; otherwise, false to keep the old text.

probably because you return true swift updates with the old text replacing the text property of the text-field you just set. Try returning false as this 'keeps the old text' which is already updated by your code.

CodePudding user response：

The reason is func shouldChangeCharactersIn call before the text is input so it is wrong. What we want in here is after the value changed, add % at the end if not have. Here is the code for do that.

// add action for value change recognized
textField.addTarget(self, action: #selector(didChangeValueTextField(textField:)), for: .editingChanged)


@objc final private func didChangeValueTextField(textField: UITextField)
    {
        let text = textField.text ?? ""
        
        if !text.hasSuffix("%") {
            textField.text! = text   "%"
            
            // make cursor position to be left 1 index because final index is %
            let newPosition = textField.position(from: textField.endOfDocument, offset: -1)!
            textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)
        }
    }