# WsHandlerMetadata

**Kind:** Interface

**Source:** [`packages/websockets/context/ws-context-creator.ts`](https://github.com/nestjs/nest/blob/master/packages/websockets/context/ws-context-creator.ts#L34)

**Part of:** [Websockets](subsystem-packages-websockets)

`WsHandlerMetadata` describes the reflected metadata required to create and invoke a WebSocket handler. It captures the handler's argument count and parameter types, and provides a module-aware function for retrieving WebSocket parameter metadata.

## Properties

| Property | Type |
|---|---|
| `argsLength` | `number` |
| `paramtypes` | `any[]` |
| `getParamsMetadata` | `(moduleKey: string) => WsParamProperties[]` |

## Diagram

```mermaid
graph LR
  A[WebSocket Gateway Handler] --> B[WsHandlerMetadata]
  B --> C[argsLength: number]
  B --> D[paramtypes: any[]]
  B --> E[getParamsMetadata(moduleKey)]
  E --> F[WsParamProperties[]]
  F --> G[WsContextCreator]
```

## Usage

```ts
import type { WsHandlerMetadata } from '@nestjs/websockets';

const handlerMetadata: WsHandlerMetadata = {
  argsLength: 2,
  paramtypes: [Object, Object],
  getParamsMetadata: (moduleKey) => {
    if (moduleKey !== 'chat-module') {
      return [];
    }

    return [
      {
        index: 0,
        data: undefined,
        pipes: [],
        factory: /* WebSocket parameter factory */,
      },
    ];
  },
};

// Pass metadata to the WebSocket context creation flow.
const paramsMetadata = handlerMetadata.getParamsMetadata('chat-module');
```

## AI Coding Instructions

- Preserve `argsLength` so generated handler argument arrays match the original method signature.
- Keep `paramtypes` aligned with the reflected parameter types for the gateway handler method.
- Implement `getParamsMetadata` as module-aware; metadata may differ based on the resolved `moduleKey`.
- Return an empty `WsParamProperties[]` when no parameter decorators or metadata apply.
- Integrate this metadata with `WsContextCreator` when constructing pipes, extracting socket payloads, or resolving decorated parameters.

## Relationships

- IMPORTS → `CUSTOM_ROUTE_ARGS_METADATA`
- IMPORTS → `PARAMTYPES_METADATA`
- IMPORTS → `ContextType`
- IMPORTS → `Controller`
- IMPORTS → `PipeTransform`
- IMPORTS → `isEmpty`
- IMPORTS → `FORBIDDEN_MESSAGE`
- IMPORTS → `GuardsConsumer`
- IMPORTS → `GuardsContextCreator`
- IMPORTS → `ContextUtils`
- IMPORTS → `ParamProperties`
- IMPORTS → `ExecutionContextHost`
- IMPORTS → `HandlerMetadataStorage`
- IMPORTS → `ParamsMetadata`
- IMPORTS → `InterceptorsConsumer`
- IMPORTS → `InterceptorsContextCreator`
- IMPORTS → `PipesConsumer`
- IMPORTS → `PipesContextCreator`