# InstanceLink

**Kind:** Interface

**Source:** [`packages/core/injector/instance-links-host.ts`](https://github.com/nestjs/nest/blob/master/packages/core/injector/instance-links-host.ts#L10)

**Part of:** [Core](subsystem-packages-core)

`InstanceLink` describes a resolved dependency entry managed by the injector. It connects an injection `token` to its `InstanceWrapper`, the module-level wrapper `collection` where it was found, and the owning `moduleId` for module-aware resolution.

## Properties

| Property | Type |
|---|---|
| `token` | `InjectionToken` |
| `wrapperRef` | `InstanceWrapper<T>` |
| `collection` | `Map<any, InstanceWrapper>` |
| `moduleId` | `string` |

## Diagram

```mermaid
graph LR
  Token[InjectionToken] --> Link[InstanceLink]
  Link --> Wrapper[InstanceWrapper<T>]
  Link --> Collection[Map<any, InstanceWrapper>]
  Link --> ModuleId[moduleId: string]
  Collection --> Wrapper
```

## Usage

```ts
import { InstanceLink } from './instance-links-host';
import { InstanceWrapper } from './instance-wrapper';

function inspectLink<T>(link: InstanceLink<T>) {
  console.log(`Resolved token from module: ${link.moduleId}`);
  console.log('Token:', link.token);
  console.log('Wrapper:', link.wrapperRef);

  // The collection contains all provider wrappers for the owning module.
  const registeredWrapper = link.collection.get(link.token);

  return registeredWrapper ?? link.wrapperRef;
}

// Typically created internally by the injector during dependency resolution.
const link: InstanceLink<MyService> = {
  token: MyService,
  wrapperRef: myServiceWrapper,
  collection: moduleProviders,
  moduleId: 'AppModule',
};
```

## AI Coding Instructions

- Treat `wrapperRef` as the authoritative wrapper selected during dependency resolution; use `collection` when module-level lookup context is needed.
- Preserve the original `token`, including string, symbol, class, and custom injection-token values.
- Keep `moduleId` associated with the link so cross-module resolution and diagnostics retain module context.
- Do not assume `collection.get(token)` always returns the same wrapper as `wrapperRef`; aliases and lookup rules may affect resolution.

## Relationships

- IMPORTS → `InjectionToken`
- IMPORTS → `isFunction`