在 Kotlin class 中声明值的最佳方式：在 Constructor、body 或 init{}

Question

I wonder what would be the best approach for declaring values of a class in Kotlin (not necessarily in terms of performance, but also in terms of standards). Let me explain with code, here is the 3 possibilities I see:

private class Player(val editText: EditText, val state: Int, val name: String = editText.text.toString().trim()) {
    init{
        //we do some code here that read the String 'name'
    }
    //some other methods
}

private class Player(val editText: EditText, val state: Int) {
    val name: String = editText.text.toString().trim()
    init{
        //we do some code here that read the String 'name'
    }
    //some other methods
}

private class Player(val editText: EditText, val state: Int) {
    init{
        val name: String = editText.text.toString().trim()
        //we do some code here that read the String 'name'
    }
    //some other methods
}

I absolutely want to access the names of the players by calling their getter (player1.name for example). Which one is better than the other and why? (Perfomances and standards)

Answer 1

There is a distinct difference between your first option and the other two.

Option 1 - Constructor initialization:

This option, in addition to setting the "name" property automatically, also lets the creator of the object set the name via:

val myPlayer = Player(EditText(), 0, "Bob")

The other options don't allow the caller to set the name.

Option 2 and Option 3 are nearly the same, functionally. There should not be any noticeable performance differences. The biggest difference is that the code in option 2 will run before the init block.

As far as standards go:

• Pick option 1 if you want the caller to be able to set the name
• Pick option 2 if you want the name to be forced to use the "editText" object to be set

There are no hard standards, so if option 3 looks better to you and any others who will read the code, go ahead and pick that. Personally, I would only initialize fields in the init block if the initialization required code that was more complex than a basic one-liner.