# Edge

**Kind:** Interface

**Source:** [`packages/core/inspector/interfaces/edge.interface.ts`](https://github.com/nestjs/nest/blob/master/packages/core/inspector/interfaces/edge.interface.ts#L26)

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

`Edge` represents a directed relationship between two entities in the inspector graph. It identifies the connection, its source and target node IDs, and metadata describing whether the relationship is module-to-module or class-to-class.

## Properties

| Property | Type |
|---|---|
| `id` | `string` |
| `source` | `string` |
| `target` | `string` |
| `metadata` | `ModuleToModuleEdgeMetadata | ClassToClassEdgeMetadata` |

## Diagram

```mermaid
graph LR
  Source["Source entity<br/>(source)"] --> Edge["Edge<br/>id + metadata"] --> Target["Target entity<br/>(target)"]
  Edge --- Metadata["ModuleToModuleEdgeMetadata<br/>or ClassToClassEdgeMetadata"]
```

## Usage

```ts
import type { Edge } from '@core/inspector/interfaces/edge.interface';

const moduleDependency: Edge = {
  id: 'app-module->users-module',
  source: 'app-module',
  target: 'users-module',
  metadata: {
    type: 'module-to-module',
    // Additional ModuleToModuleEdgeMetadata fields
  },
};

// Use the edge when constructing an inspector dependency graph.
graph.edges.push(moduleDependency);
```

## AI Coding Instructions

- Use stable, unique `id` values so graph edges can be reliably indexed, updated, and rendered.
- Ensure `source` and `target` reference valid node IDs already present in the inspector graph.
- Provide metadata that matches the relationship type: `ModuleToModuleEdgeMetadata` for module dependencies and `ClassToClassEdgeMetadata` for class relationships.
- Treat edges as directed: `source -> target` may not represent the same relationship as `target -> source`.
- Keep edge metadata aligned with the graph consumer’s expected discriminators and rendering logic.

## Relationships

- IMPORTS → `InjectionToken`