Conditional Unity UI and dynamic lists

Dynamic helpers return retained component results. Bind them as children under a stable mount/root.

var visible = UI.Source(true);
var message = UI.Show(() => visible.Value, () => UI.Label("Hello"));
var container = UI.Column(UI.Children(() => message.Value));

The selected branch is retained while its identity stays the same. Switching identity removes the old branch immediately unless an advanced constructor supplies an exit delay.

Choose row identity

Indexes preserves fixed keys and exposes reactive row values. Its list overload uses array positions as keys. For editable records, supply permanent IDs through its keyed key/value-pair overload.

Values preserves values and exposes reactive indices. Values must be unique and non-null under the chosen comparer.

var names = UI.Source<string[]>(new[] { "Ada", "Grace" });
var rows = UI.Values<string, TMPro.TextMeshProUGUI>(
    () => names.Value,
    (name, index) => UI.Label(() => $"{index.Value + 1}. {name}"));
var list = UI.Column(UI.Children(() => rows.Value));

Membership/order changes publish new output arrays. Existing row signals can update without rebuilding those arrays. These lists retain and reconcile UI by identity.

Retained exits

Advanced constructors receive a presence source and return Branch<T>. For a fading branch:

var fading = UI.Show<UnityEngine.Component>(() => visible.Value, present =>
{
    var alpha = UI.Spring(() => present.Value ? 1f : 0f, period: 0.18);
    return new Branch<UnityEngine.Component>(
        UI.Label("Hello", UI.Opacity(alpha)), 0.35);
});
var host = UI.Column(UI.Children(() => fading.Value));

Presence becomes false on departure. The branch remains for 0.35 seconds; reentry cancels removal and reuses it. Departing Values rows receive index -1, so format indices with exit state in mind. Active rows appear before exiting rows.

Row scopes own their resources. Failed cleanup does not leave removed results published; other removals are attempted before aggregate errors are reported. Dispose the parent owner to release all rows.

Continue with animation.

Build a dynamic inventory list with stable IDs.