Scene2D builders inside constructors

[Divelix]

I have UI with several Tables that I want to put into separate classes, so I have code like that:

class MyTable: Table() {
    init {
        val subTable1 = scene2d.table { ... }
        val subTable2 = scene2d.table { ... }

        add(subTable1)
        row()
        add(subTable2)
    }
}

Can I use builders there somehow to get something like that?

class MyTable: Table() {
    init {
        table { ... } // subTable1
        row()
        table { ... } // subTable2
    }
}

[czyzby]

Yes, you have to implement the KTable interface:

import ktx.scene2d.KTable
import com.badlogic.gdx.scenes.scene2d.ui.Table

class MyTable: Table(), KTable {
  init {
    table { } // subTable1
    row()
    table { } // subTable2
  }
}

Since MyTable already extends Table, there aren't any extra methods that you have to override - all you have to do is to add the interface.

Similar interfaces exist for groups, trees, etc.

[Divelix]

Awesome! I had gut feelling that it is possible)

[czyzby]

I added a similar example to the README. Thanks.

[Divelix]

I just found out that in this case I can't use class fields, like:

I faced this problem in #301, but in that case I just refused using KGroup. How can I fix that and keep using KGroup?

[czyzby]

@Divelix This is because this is changed via the DSL to prevent from accessing nested properties. If you need to access a class property within the constructor, add an explicit receiver: this@ClassName. - for example:

import com.badlogic.gdx.scenes.scene2d.Group

class Try: Group(), KGroup {
  val str = "text"
  
  init {
    table { 
      label(this@Try.str)
    }
  }
}

[czyzby]

Just wanted to say that this is an expected side effect of the Kotlin DSL builders, and it actually has some advantages. For example, you cannot immediately access properties of parent actors within the children blocks:

table {
  label("Child") {
    // This will not compile, so you will not modify the table accidentally:
    pad(2f)
    // If you really need to access parent's properties, you can do so explicitly:
    this@table.pad(2f)
  }

  // This compiles normally, as we're within the table block:
  pad(2f)
}