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# RegisterFunctionDeclaration(string,Type,Type\[])

Method in [IActionRegistration](/3.1/api/csharp/yarn.unity/yarn.unity.iactionregistration.md)

## Summary

Registers a function as existing, without supplying an implementation.

```csharp
void RegisterFunctionDeclaration(string name, Type returnType, Type[] parameterTypes);
```

## Parameters

| Name                    | Description                             |
| ----------------------- | --------------------------------------- |
| `string` name           | The name of the function.               |
| `Type` returnType       | The return type of the function.        |
| `Type[]` parameterTypes | The types of the function's parameters. |