Greeter

The user types a name and the greeting updates on every keystroke. No buttons, no bootstrap code.

You learn: MonoViewModel, [TwoWayBind], [BindAlso], On*Changed hooks.

Assumes: Counter.

Scene: Scenes/Greeter.unity. Script: Scripts/GreeterMonoViewModel.cs.

What we build

[ Type a name... ]   →   Hi, Vlad!     [ Clear ]
    InputField             Text

Two directions of data

Counter moved data one way: ViewModel → UI. Here the input field writes back:

ViewModel ──────────► UI      OneWay:  Greeting
ViewModel ◄─────────► UI      TwoWay:  Name

ViewModel on a GameObject

[ViewModel]
public sealed partial class GreeterMonoViewModel : MonoViewModel
{
    [BindAlso(nameof(Greeting))]
    [TwoWayBind]
    [SerializeField] private string _name;

    private string Greeting =>
        string.IsNullOrEmpty(Name)
            ? string.Empty
            : $"Hi, {Name}!";

    [RelayCommand]
    private void Clear() =>
        Name = string.Empty;
}

• MonoViewModel is a component. ViewInitializer in the scene connects it to the MonoView, so there is no Bootstrap.
• [TwoWayBind] lets the InputFieldMonoBinder write into Name.
• [BindAlso(nameof(Greeting))] re-sends the computed Greeting whenever Name changes. The property itself needs no attribute.
• Clear sets Name from the ViewModel side; because the binding is two-way, the input field empties too.

	[OneWayBind]	[TwoWayBind]
ViewModel → UI	yes	yes
UI → ViewModel	no	yes
Typical binders	Text, counters, state	InputField, Toggle, Slider

The other way: On*Changed

When the reaction is an action rather than a derived value, use the generated hook instead of [BindAlso]:

[ViewModel]
public sealed partial class GreeterViewModel
{
    [TwoWayBind] private string _name = "";
    [OneWayBind] private string _greeting = "Type a name";

    partial void OnNameChanged(string newValue) =>
        Greeting = string.IsNullOrEmpty(newValue) ? "Type a name" : $"Hi, {newValue}!";
}

The generator declares partial void OnNameChanged(string newValue) and calls it from the Name setter. The whole chain is direct calls:

InputField changed → binder sets Name → OnNameChanged → Greeting set → TextMonoBinder updates

Both styles are fine. [BindAlso] reads better for derived values, On*Changed for side effects.

Scene

Greeter
├── GreeterMonoViewModel   (GreeterMonoViewModel.cs)
└── Greeter UI
    ├── MonoView + ViewInitializer
    ├── Name Input         (TMP_InputField + InputFieldMonoBinder)
    ├── Greeting Text      (TextMonoBinder)
    └── Clear Button       (Button + ButtonCommandMonoBinder)

ViewInitializer points at the GreeterMonoViewModel component and the MonoView. The MonoView lists binders by id (Name, Greeting, ClearCommand).

Styling the greeting with converters

Coloring the name is a View concern, so it does not belong in the ViewModel. TextMonoBinder has a Converter slot. Pick Aspid → Composition → Sequence and add two links:

1. Aspid → String → Rich Text Color wraps the text in a <color> tag.
2. Aspid → String → String Format with {0}! appends an exclamation mark outside the tag.

warning

TextMeshPro executes markup inside any string. If Name can be seen by other players, put RichTextSanitizeConverter or RichTextNoParseConverter first in the chain.

Summary

Concept	What we did
MonoViewModel	ViewModel as a component, wired by ViewInitializer
[TwoWayBind]	Name syncs with the input field in both directions
[BindAlso]	Greeting re-sent on every Name change
On*Changed	Reaction hook without explicit subscriptions
Converters	Formatting stays in the View

Next: Bind Modes, all four modes on one screen.

Text uses TextMeshPro (part of com.unity.ugui). The sample ships its own font asset in Fonts/ (Liberation Sans, OFL), so it does not depend on the fonts from TMP Essentials.