Allow user to delete textfield text but restrict maximum text length

Question

I have UITextField and i want allow user to type only up to 4 symbols. But i also want to allow them to erase symbols with keyboard (i mean, delete last and move caret for left. Symbol look like rectangle left arrow with cross on iOS keyboard).

For now i ended up with:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    guard let text = textField.text, text.count < 4 else { return false }
    return true
  }

But i have no idea, how to let users to delete symbols. When text count become 4, i am not allowed to type or do any actions.

score 3 · Answer 1 · answered May 31 '19 at 10:55

From the docs of textField(_:shouldChangeCharactersIn:replacementString:)

When the user deletes one or more characters, the replacement string is empty.

Thus, all you're missing is to check if the replacement string is empty:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    return string.isEmpty || (textField.text?.count ?? 0) < 4
}

m1sh0 · Answer 2 · 2019-05-31T11:47:04.487

2

use this

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    return textField.text!.count + string.count < 5
}

edited May 31 '19 at 11:47

answered May 31 '19 at 10:55

m1sh0

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I will appreciate the reason why I have a negative vote on my answer !!! – m1sh0 May 31 '19 at 10:57
1

With your code, user can insert some characters at position less than 4 even when the text length exceeds 4. – OOPer May 31 '19 at 11:02
Thanks @OOPer you are right. – m1sh0 May 31 '19 at 11:04
great answer, better than what I found in the linked thread. – Iskeraet Dec 11 '20 at 17:36

score 0 · Answer 3 · edited May 31 '19 at 12:32

0

You have to check the length in the should change character in range method. Like following

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let newLength = textField.text.length + (string.length - range.length)

    if newLength <= maxLength {
       return true
    } else {
       return false 
    }
}

Here maxLength is the maximum length of chracters which you want to allow

edited May 31 '19 at 12:32

VishalPethani

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answered May 31 '19 at 10:56

Waqar Khalid

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Your code does not compile. – OOPer May 31 '19 at 11:06

Ahemadabbas Vagh · Answer 4 · 2019-05-31T11:13:01.443

0

You can use below code to get updated string and compare with that to your length,

func textField(_ textFieldToChange: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
  // limit to 4 characters
  let characterCountLimit = 4

  // We need to figure out how many characters would be in the string after the change happens
  let startingLength = textFieldToChange.text?.count ?? 0
  let lengthToAdd = string.count
  let lengthToReplace = range.length

  let newLength = startingLength + lengthToAdd - lengthToReplace

  return newLength <= characterCountLimit
}

edited May 31 '19 at 11:13

answered May 31 '19 at 11:05

Ahemadabbas Vagh

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Your `currentText` may be wrong when range is not empty. – OOPer May 31 '19 at 11:06
try this if anything goes wrong then let me know – Ahemadabbas Vagh May 31 '19 at 11:07
Fill 4 characters, select all, then input one character. – OOPer May 31 '19 at 11:08
try this updated code – Ahemadabbas Vagh May 31 '19 at 11:13
Improved, but equivalent to the Swift code of the approved answer in the link. – OOPer May 31 '19 at 11:15

Allow user to delete textfield text but restrict maximum text length

4 Answers4