Components with Define

Define wraps a render closure into a component. The closure is called every time Gova needs to (re)render the component; between renders it preserves state, effects, and provided stores.

func Define(fn func(*Scope) View) View

Use Define for the top-level App and for tiny one-off views. If the component needs parameters, prefer a Viewable struct so callers pass typed field values rather than closure captures.

Example

var Counter = gova.Define(func(s *gova.Scope) gova.View {
	count := gova.State(s, 0)
 
	return gova.VStack(
		gova.Text(count.Format("count: %d")).Font(gova.Title),
		gova.Button("+1", func() {
			count.Update(func(n int) int { return n + 1 })
		}),
	).Spacing(gova.SpaceSM)
})

The closure captures nothing external. All mutable values (here count) live on the *Scope, which survives across renders. If you declare a local variable in the closure without routing it through State, Ref, or a store, it is recreated on every render and does not participate in reactivity.

Re-rendering

A component rerenders when any StateValue or store it reads is mutated via Set or Update. The render is scheduled on the UI goroutine through Fyne's fyne.Do, so state can be mutated from any goroutine safely.

Limitations

A Define-based component has no way to accept parameters. Any reusable component that takes arguments should be a Viewable struct.