BaseObservableExt.kt

import android.databinding.BaseObservable
import kotlin.properties.Delegates

fun <T> BaseObservable.dataBind(defaultValue: T, fieldId: Int, vararg fieldIds: Int, callback: ((oldValue: T, newValue: T) -> Unit)? = null) =
    Delegates.observable(defaultValue) { _, old, new ->
        if (old != new) {
            callback?.invoke(old, new)
            notifyPropertyChanged(fieldId)
            fieldIds.forEach { notifyPropertyChanged(it) }
        }
    }

fun <T> BaseObservable.dataBindAction(noOpValue: T, fieldId: Int, callback: ((oldValue: T, newValue: T) -> Unit)? = null) =
    Delegates.observable(noOpValue) { _, old, new ->
        if (new != noOpValue) {
            callback?.invoke(old, new)
            notifyPropertyChanged(fieldId)
        }
    }