Bind

Value binding allows you to link the value of a variable and the value of a widget, ensuring that they automatically stay up-to-date.

For example, the update example can also be written as:

count := 0
text := core.Bind(&count, core.NewText(b))
core.NewButton(b).SetText("Increment").OnClick(func(e events.Event) {
    count++
    text.Update()
})

That code uses core.Bind to bind the value of the variable count to the text of the widget text, meaning that the text will be updated from the variable whenever core.WidgetBase.Update is called.

You can use value binding with more than just text widgets; most widgets implement the core.Value interface and thus support value binding. For example, this code uses value binding with a switch and a corresponding bool value:

on := true
core.Bind(&on, core.NewSwitch(b)).OnChange(func(e events.Event) {
    core.MessageSnackbar(b, "The switch is now "+strconv.FormatBool(on))
})

Note that value binding goes both ways: not only is the value of the widget updated in core.WidgetBase.Update, the value of the bound variable is updated on change events. This two-way updating makes value binding very useful for creating interactive widgets that represent some underlying value.