Bind Modes

Every BindMode on one screen, plus a converter of your own in a binder slot.

You learn: OneTime, OneWay, TwoWay, OneWayToSource; several binders on one member; ITwoWayConverter.

Assumes: Greeter.

Scene: Scenes/Bind Modes.unity. Scripts: Scripts/ViewModels/AudioSettingsViewModel.cs, Scripts/Converters/PerceptualVolumeConverter.cs.

What we build

OneTime          1.0.0
OneWay           Normal
TwoWay           [────●────] 0.5     [x] Muted
OneWayToSource   [ Profile name...  ]
                 [ Reset ]

Four modes, four fields

[ViewModel]
[Serializable]
public sealed partial class AudioSettingsViewModel
{
    [OneTimeBind] private readonly string _version = "1.0.0";

    [BindAlso(nameof(VolumeLabel))]
    [TwoWayBind]
    [SerializeField] [Range(0f, 1f)] private float _volume = 0.5f;

    [TwoWayBind]
    [SerializeField] private bool _isMuted;

    [OneWayToSourceBind] private string _profileName;

    [RelayCommand]
    private void Reset()
    {
        Volume = 0.5f;
        IsMuted = false;
    }

    private string VolumeLabel => Volume switch
    {
        0f => "Silent",
        < 0.34f => "Quiet",
        < 0.67f => "Normal",
        _ => "Loud",
    };

    partial void OnProfileNameChanged(string newValue) =>
        Debug.Log($"Profile name is now \"{newValue}\"");
}

Member	Mode	Who writes	Binder in the scene
`Version`	`OneTime`	nobody after the first read	Text
`VolumeLabel`	`OneWay`	ViewModel → View	Text
`Volume`	`TwoWay`	both	Slider, Text
`IsMuted`	`TwoWay`	both	Toggle, slider `interactable`
`ProfileName`	`OneWayToSource`	View → ViewModel	Input field

The mode declared on the ViewModel member is the upper bound. Each binder picks its own mode in the Mode field, but never above what the member allows: a OneWay text on a TwoWay property is fine, a TwoWay slider on a OneWay property is rejected by the editor.

A readonly field becomes OneTime on its own. [OneTimeBind] is spelled out here for clarity.

One member, several binders

Volume is bound twice: the slider (TwoWay) and a label (OneWay). IsMuted is bound twice as well: the toggle (TwoWay) and the slider's interactable through SelectableInteractableMonoBinder with a BoolInvertConverter in its slot. While muted, the slider is disabled.

The ViewModel describes state once. How many UI elements look at it is up to the scene.

Your own converter

[Serializable]
[TypeSelectorDisplay(Group = "Samples/Bind Modes", Name = "Perceptual Volume")]
public sealed class PerceptualVolumeConverter : ITwoWayConverter<float, float>
{
    [SerializeField] [Min(0.1f)] private float _exponent = 2f;

    public float Convert(float value) => Mathf.Pow(Mathf.Clamp01(value), 1f / _exponent);
    public float ConvertBack(float value) => Mathf.Pow(Mathf.Clamp01(value), _exponent);
}

[Serializable] lets the converter live in a binder's [SerializeReference] slot.
[TypeSelectorDisplay] puts it into the Converter dropdown in the Inspector.
ITwoWayConverter is required for a TwoWay binder. Without ConvertBack the slider value would reach the ViewModel unconverted, and the binder warns about it in the console.

It sits in the SliderValueMonoBinder slot: linear volume 0.25 shows as slider position 0.5 and back.

Summary

Concept	Where
Four `BindMode`s	one field per mode
Binder mode ≤ member mode	the Mode field of every binder
Several binders per member	`Volume`, `IsMuted`
Built-in converter	`BoolInvertConverter` on `interactable`
Own `ITwoWayConverter`	`PerceptualVolumeConverter`

What we build​

Four modes, four fields​

One member, several binders​

Your own converter​

Summary​

What we build

Four modes, four fields

One member, several binders

Your own converter

Summary