---
id: fast-foundation.interfacesymbol
title: InterfaceSymbol type
hide_title: true
---
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[@microsoft/fast-foundation](./fast-foundation.md) &gt; [InterfaceSymbol](./fast-foundation.interfacesymbol.md)

## InterfaceSymbol type

A constant key that can be used to represent an interface to a registered dependency. The key can be used in DI registrations but also doubles as a decorator for resolving the associated, registered dependency.

<b>Signature:</b>

```typescript
export declare type InterfaceSymbol<K = any> = (target: any, property: string, index?: number) => void;
```