Swift : Error: 'required' initializer 'init(coder:)' must be provided by subclass of 'UIView'

Question

I have a problem when I build my app in swift 2. Xcode says:

'required' initializer 'init(coder:)' must be provided by subclass of 'UIView'

This is the code of the class :

class creerQuestionnaire: UIView {
  @IBOutlet weak var nomQuestionnaire: UITextField!
  @IBOutlet weak var question: UITextField!
  @IBOutlet weak var reponse: UITextField!
  var QR: Questionnaire

  @IBAction func creerQuestion(sender: AnyObject) {
    QR.ajouterQuestion(question.text!, nouvReponse: reponse.text!)
  }
}

and this is the class Questionnaire:

import Foundation

class Questionnaire {
  var QR = [String(), String()]

  func getQuestion(nbQuestion: Int) ->String {
    return QR[nbQuestion]
  }

  func getReponse(nbReponse: Int) ->String {
    return QR[nbReponse]
  }

  func ajouterQuestion(nouvQuestion: String, nouvReponse: String) {
    QR += [nouvQuestion, nouvReponse]
  }
}

Merci!

Allen · Accepted Answer · 2016-02-07 15:50:54Z

26

Note for required: Write the required modifier before the definition of a class initializer to indicate that every subclass of the class must implement that initializer.

Note for override: You always write the override modifier when overriding a superclass designated initializer, even if your subclass’s implementation of the initializer is a convenience initializer.

Above both notes are referred from: Swift Programming Language/Initialization

Therefore, your subclass of UIView should look similar to the sample below:

class MyView: UIView {
    ...
    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    ...
}

edited Feb 7, 2016 at 15:50

answered Feb 7, 2016 at 15:44

Allen

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3 Comments

Michael Dautermann Over a year ago

why is one override and the other required?

Allen Over a year ago

@MichaelDautermann I just added some information about required and override. Thanks for highlight.

R1' Over a year ago

Thanks for reply !

Chenghui He · Accepted Answer · 2024-03-06 06:27:11Z

3

According to the latest swift syntax, the init method needs to add methods：

required init?(coder aDecoder: NSCoder) 
{

    fatalError("init(coder:) has not been implemented")
}

edited Mar 6, 2024 at 6:27

answered Dec 18, 2017 at 6:00

Chenghui He

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Comments

claude31 · Accepted Answer · 2017-11-10 22:48:44Z

1

Some comments to this code:

var QR = [String(), String()]

a var name should begin with lowercase : var qr

Do you want to initialize with 2 empty strings ? In your code, you get ["", ""] at init. This array will not be very convenient to use, because you mix question and answer in sequence.

Would probably be better to create an array of pairs :

var qr : [(q: String, r: String) = [] // initiated as empty

you access to its components by : qr[i].q and qr[i].r

You need to test that nbQuestion is in bounds ; with the previous definition of qr, that would be

func getQuestion(nbQuestion: Int) ->String {
    if nbQuestion < 0 || nbQuestion >= qr.count { return "" }
    return qr[nbQuestion].q
}

Note: nbReponse and nbQuestion share the same value for a given qr

func getReponse(nbReponse: Int) ->String {
   if nbReponse < 0 || nbReponse >= qr.count { return "" }
      return qr[nbReponse].r
}

func ajouterQuestion(nouvQuestion: String, nouvReponse: String) {
    qr += [(nouvQuestion, nouvReponse)]
}

answered Nov 10, 2017 at 22:48

claude31

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1 Comment

ReinstateMonica3167040 Over a year ago

That type should be [(q: String, r: String)] for qr - you're missing a bracket

Umer Hassam · Accepted Answer · 2016-02-08 07:06:05Z

-3

Non-Optional variables must be initialised with a value...

Either Declare QR as an optional

var QR: Questionnaire?

OR initialise it:

var QR: Questionnaire = Questionnaire()

answered Feb 8, 2016 at 7:06

Umer Hassam

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