Question: This is my function declaration:

```
fun MyDialog(ctx: Context, msg: String, yestext: String = "", OnYes: DialogInterface.OnClickListener): AlertDialog

```

How do i set a default value for "OnYes: DialogInterface.OnClickListener"?

I have tried OnYes: DialogInterface.OnClickListener = null but it doesn't work.

Answer: 
Answer provided by @mangkool

OnYes: DialogInterface.OnClickListener? = null
```
val builder = AlertDialog.Builder(this@MainActivity)

            // Set the alert dialog title
            builder.setTitle("App background color")

            // Display a message on alert dialog
            builder.setMessage("Are you want to set the app background color to RED?")

            // Set a positive button and its click listener on alert dialog
            builder.setPositiveButton("YES"){dialog, which ->
                // Do something when user press the positive button
                Toast.makeText(applicationContext,"Ok, we change the app background.",Toast.LENGTH_SHORT).show()

                // Change the app background color
                root_layout.setBackgroundColor(Color.RED)
            }

            // Display a negative button on alert dialog
            builder.setNegativeButton("No"){dialog,which ->
                Toast.makeText(applicationContext,"You are not agree.",Toast.LENGTH_SHORT).show()
            }

            // Display a neutral button on alert dialog
            builder.setNeutralButton("Cancel"){_,_ ->
                Toast.makeText(applicationContext,"You cancelled the dialog.",Toast.LENGTH_SHORT).show()
            }

            // Finally, make the alert dialog using builder
            val dialog: AlertDialog = builder.create()

            // Display the alert dialog on app interface
            dialog.show()

```