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Custom Commands

Command represents a single operation, that controls what happens on the scene; e.g., it can be used to change a background, move a character or load another naninovel script. Parametrized command sequences defined in naninovel scripts effectively controls the game flow. You can find available built-in commands in the API reference. In code, all the built-in script command implementations are defined under Naninovel.Commands namespace.

Adding Custom Command

To add your own custom script command, create a new C# class derived from Command and implement ExecuteAsync abstract method. The created class will automatically be picked up by the engine and you'll be able to invoke the command from the naninovel scripts by either the class name or an alias (if assigned). To assign an alias to the naninovel command, apply CommandAlias attribute to the class.

Below is an example of a custom command, that can be invoked from naninovel scripts as @HelloWorld or @hello to print "Hello World!" to the console and can also take an optional name parameter (eg, @hello name:Felix) to greet the provided name instead of the world.

using Naninovel;
using Naninovel.Commands;
using UnityEngine;

public class HelloWorld : Command
    public StringParameter Name;

    public override UniTask ExecuteAsync (AsyncToken asyncToken = default)
        if (Assigned(Name)) Debug.Log($"Hello, {Name}!");
        else Debug.Log("Hello World!");
        return UniTask.CompletedTask;


When adding custom implementation types under a non-predefined assembly (via assembly definitions ↗), add the assembly name to the Type Assemblies list found in the engine configuration menu. Otherwise, the engine won't be able to locate your custom types.

Execute Method

ExecuteAsync is an async method invoked when the command is executed by the scripts player; put the command logic there. Use engine services to access the engine built-in systems. Naninovel script execution will halt until this method returns a completed task in case Wait parameter is true.


Notice the optional AsyncToken argument provided for the ExecuteAsync method. When performing async operations ↗, make sure to check the token for cancellation and completion requests after each async operation and react accordingly:

  • AsyncToken.Canceled means the engine has been destroyed or reset; in both cases it's no longer safe to use the engine APIs and any state mutations will lead to an undefined behaviour. When canceled, the command implementation is expected to throw AsyncOperationCanceledException immediately, discarding any currently performed activities.
  • AsyncToken.Completed means the command is expected to complete all the activities as fast as possible; eg, if you're running animations, finish them instantly, no matter the expected duration. This usually happens when player activates continue input or a save game operation is started.
public override async UniTask ExecuteAsync (AsyncToken asyncToken = default)
    await PerformSomethingAsync();
    // Engine may have been destroyed while the above method was running;
    // below will check and throw the exception if that's the case.
    // It's safe to continue using engine APIs after the check.
    var someUI = Engine.GetService<IUIManager>().GetUI<SomeUI>();
    // In case completion is requested, fade the UI instantly.
    var fadeDuration = asyncToken.Completed ? 0 : 5;
    await someUI.ChangeVisibilityAsync(false, fadeDuration, asyncToken);
    // Notice method above accepted the token; such methods will handle
    // cancellations internally, so you don't have to check after them.

Parameter Types

To expose a command parameter to naninovel scripts, add a public field to the command class with one of the supported types:

Field TypeValue TypeScript Example
StringParameterStringLoremIpsum, "Lorem ipsum"
LocalizableTextParameterLocalizableText"Lorem ipsum|#id|"
IntegerParameterInt3210, 0, -1
DecimalParameterSingle0.525, -55.1
BooleanParameterBooleantrue, false
NamedStringParameterNamedStringScript001.LabelName, .LabelName
StringListParameterList<String>Lorem,ipsum,"doler sit amet"

Parameter Alias

Optionally, you can apply [ParameterAlias] attribute to the field to assign an alias name to the parameter allowing it to be used instead of the field name when referencing the parameter in naninovel scripts. If you wish to make the parameter nameless, set NamelessParameterAlias constant (empty string) as the alias; please note, that only one nameless parameter is allowed per command.

public StringParameter MyNamelesParameter;
public StringParameter MyParameter;
@cmd "value of the nameless param" myParam:"value of 'MyParameter' param"

Required Parameter

To make parameter required (causing an error to be logged when it's not specified in naninovel script), apply [RequiredParameter] attribute to the field. When the attribute is not applied, parameter is considered optional.

public StringParameter MyRequiredParameter;

Optional Parameter

When parameter is not required, it may or may not have value assigned in the scenario script; use HasValue property to test whether that's the case. Optionally, you can use Assigned() static method, which takes parameter instance and returns true when the provided parameter is not null and has a value assigned.

public StringParameter MyOptionalParameter;
if (MyOptionalParameter.HasValue) { }
if (Assigned(MyOptionalParameter)) { }

Localizable Command

In case the command has parameters that can be localized (text directly presented to the user, usually), implement Command.ILocalizable interface to add the command to the generated script localization documents and use LocalizableTextParameter parameter type.

public class PrintText : Command, Command.ILocalizable
    public LocalizableTextParameter Text;

Preloadable Command

In case execution of the command requires loading some resources, implement Command.IPreloadable interface to preload the required resources when the game is loading; find more about memory management in the resource providers guide.

public class PlayAudioClip : Command, Command.IPreloadable
    public StringParameter ClipPath;

    public async UniTask PreloadResourcesAsync ()
        if (!Assigned(ClipPath) || ClipPath.DynamicValue) return;
        await ... (load the audio clip here)

    public void ReleasePreloadedResources ()
        if (!Assigned(ClipPath) || ClipPath.DynamicValue) return;
        ... (unload the clip here)

Notice ClipPath.DynamicValue check: we wouldn't be able to preload the resource in case the name is only known when the command is executed (ie parameter contain script expressions); in this case the resource should be loaded inside ExecuteAsync method.

Command Examples

You can find scripts with all the built-in command implementations at Naninovel/Runtime/Commands package folder; feel free to use them as a reference when implementing your own custom commands.


Another example of adding custom commands to add/remove items of an inventory system can be found in the inventory example project on GitHub ↗.

Specifically, the command implementations are stored at Runtime/Commands ↗ directory.

Overriding Built-In Command

In some cases it could be useful to override built-in Naninovel commands. For example, you may want to change how @print commands work without adding a custom one, so that the change will also affect generic text lines (text from the generic lines is parsed into the print commands under the hood).

To override a built-in command, add a custom one and apply the same alias built-in command has. Reimport the naninovel scripts (right-click over a folder they're stored at, then click "Reimport") after overriding a command in order for the changes to take effect. The custom command will then automatically be used instead of the built-in one when playing a naninovel script.

Below is an example of overriding built-in @print command, so that the printed text will be logged into the console before being revealed to the player.

public class MyCustomPrintCommand : PrintText
    public override UniTask ExecuteAsync (AsyncToken asyncToken = default)
        return base.ExecuteAsync(asyncToken);


Find a more useful example of overriding built-in commands on the forum ↗. An overridden and custom commands will allow changing reveal speed right inside generic text lines, eg:

Yuko: [s 0.1] Print text 10 times slower than usual. [s 2] Print 2 times faster.