Kotlin Extension Function

Question

Considering this:

MyView.setVisibility(View.VISIBLE)

can be simplified to this:

inline fun View.setVisible() = apply { visibility = View.VISIBLE }

MyView.setVisible()

Or this if you prefer:

inline infix fun View.vis(vis: Int) = apply { visibility = vis }
MyView vis View.VISIBLE

Is there anyway of accomplish the same by doing this:

MyView.VISIBLE

mfulton26 · Accepted Answer · 2016-07-07T15:41:28.970

5

It seems a bit odd for a "getter" to modify state but you can use an extension property:

val View.VISIBLE: Unit
    get() {
        visibility = View.VISIBLE
    }

And you could also make it return the new visibility value or return itself so that you can potentially chain calls.

val View.VISIBLE: Int
    get() {
        visibility = View.VISIBLE
        return visibility
    }

or

val View.VISIBLE: View
    get() = apply { visibility = View.VISIBLE }

edited Jul 07 '16 at 15:41

answered Jul 07 '16 at 15:35

mfulton26

29,956
6
64
88

1

yes you right it is weird. This is not a real scenario, was just messing around with stuff. Thanks – johnny_crq Jul 07 '16 at 15:39

hotkey · Answer 2 · 2016-07-07T15:47:24.987

2

Yes, you can write an extension property property with a getter like this:

val View.visible: View
    get() = apply { visibility = View.VISIBLE }

With the usage:

 myView.visible

However, keep in mind that properties with side effects in getters are generally discouraged (see also: Functions vs Properties), and this behavior is rather confusing for a property.

edited Jul 07 '16 at 15:47

answered Jul 07 '16 at 15:38

hotkey

140,743
39
371
326

Kotlin Extension Function

2 Answers2