UITextFieldDelegate method not called

问题

I'm following the Big Nerd Ranch iOS Programming book (Swift version) and I have this file.

import UIKit

class ConversionViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet var celsiusLabel: UILabel!
    @IBOutlet var textField: UITextField!

    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        print("here")
        return true
    }

    //rest of the code here
}

For some reason, the textField delegate method is not called. I can't see the "here" log in my console. I have double checked the naming and syntax a lot of times. Any ideas?

回答1:

You need set delegate of your text field to self.

override func viewDidLoad() {
     super.viewDidLoad()
     textField.delegate = self
}

回答2:

Is this line present?

textField.delegate = self

回答3:

I was missing a _ in my function, after the first parenthesis:

This doesn't work:

func textFieldDidBeginEditing(textField: UITextField) {
}

This works:

func textFieldDidBeginEditing(_textField: UITextField) {
}

回答4:

you have to follow these step --

1- put delegate with class name .

class YourViewController: UIViewController,UITextFieldDelegate

2- assign the delegate in viewDidLoad method.

textField.delegate = self

3- add the delegate method --

func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool
{
    // return NO to disallow editing.
    return true
}

func textFieldDidBeginEditing(_ textField: UITextField)
{
    // became first responder
}

func textFieldShouldEndEditing(_ textField: UITextField) -> Bool
{
    // return YES to allow editing to stop and to resign first responder status. NO to disallow the editing session to end
    return true
}

func textFieldDidEndEditing(_ textField: UITextField)
{
    // may be called if forced even if shouldEndEditing returns NO (e.g. view removed from window) or endEditing:YES called
}

func textFieldDidEndEditing(_ textField: UITextField, reason: UITextFieldDidEndEditingReason)
{
    // if implemented, called in place of textFieldDidEndEditing:
}

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool
{
    // return NO to not change text
    return true
}


func textFieldShouldClear(_ textField: UITextField) -> Bool
{
    // called when clear button pressed. return NO to ignore (no notifications)
    return true
}

回答5:

For this function:

func textFieldDidBeginEditing(_textField: UITextField) { }

make sure you don't mark it as private. e.g. don't to this:

private func textFieldDidBeginEditing(_textField: UITextField) { }

It won't get called if marked private.

来源：https://stackoverflow.com/questions/34842153/uitextfielddelegate-method-not-called

标签

ios

swift

uitextfield