ExecutionContextHost

Kind: Class

Source: packages/core/helpers/execution-context-host.ts

Part of: Core

ExecutionContextHost is the concrete implementation of Nest’s execution context abstraction. It stores the current invocation arguments, controller class, handler function, and transport type, then exposes transport-specific views for HTTP, RPC, and WebSocket execution.

Implements: ExecutionContext

Methods

Diagram

mermaid
graph LR
  A[Invocation Arguments] --> B[ExecutionContextHost]
  C[Controller Class] --> B
  D[Handler Method] --> B

  B --> E[getArgs / getArgByIndex]
  B --> F[getClass / getHandler]
  B --> G[setType / getType]

  B --> H[switchToHttp]
  B --> I[switchToRpc]
  B --> J[switchToWs]

  H --> K[HttpArgumentsHost]
  I --> L[RpcArgumentsHost]
  J --> M[WsArgumentsHost]

Usage

ts
import { ExecutionContextHost } from '@nestjs/core/helpers/execution-context-host';

class UsersController {
  findOne() {
    return { id: 1 };
  }
}

const request = { params: { id: '1' } };
const response = {};
const next = () => undefined;

const context = new ExecutionContextHost(
  [request, response, next],
  UsersController,
  UsersController.prototype.findOne,
);

context.setType('http');

const http = context.switchToHttp();

console.log(context.getType()); // "http"
console.log(context.getClass()); // UsersController
console.log(context.getHandler()); // findOne
console.log(http.getRequest().params.id); // "1"

AI Coding Instructions

• Preserve argument ordering when creating a context: HTTP uses [request, response, next], while RPC and WebSocket adapters use transport-specific argument positions.
• Call setType() when manually constructing a host so guards, interceptors, and metadata consumers can identify the active transport.
• Use switchToHttp(), switchToRpc(), or switchToWs() instead of directly indexing arguments when writing transport-aware integrations.
• Treat getClass() and getHandler() as metadata lookup targets for decorators, reflection, guards, and interceptors.
• Avoid reusing one ExecutionContextHost instance across unrelated requests or message handlers.

How it works

ExecutionContextHost is a concrete ExecutionContext implementation that stores a handler argument array, an optional class reference, an optional handler reference, and a mutable context-type string. Its initial context type is 'http'. [packages/core/helpers/execution-context-host.ts:10-17]

• Its constructor accepts args, constructorRef, and handler; the latter two default to null. [packages/core/helpers/execution-context-host.ts:13-17]
• getArgs() returns the stored argument array, and getArgByIndex(index) reads the element at that index. [packages/core/helpers/execution-context-host.ts:35-41]
• getClass() returns the stored class reference and getHandler() returns the stored handler reference. Both use TypeScript non-null assertions, although their constructor values may be null when omitted. [packages/core/helpers/execution-context-host.ts:13-17] [packages/core/helpers/execution-context-host.ts:27-33]
• setType(type) replaces the stored context type only when type is truthy; a falsy value leaves the existing type unchanged. getType() returns the stored value. [packages/core/helpers/execution-context-host.ts:19-25]
• switchToRpc() assigns getData() and getContext() methods onto the host itself and returns that same object; those methods read argument indexes 0 and 1, respectively. [packages/core/helpers/execution-context-host.ts:43-48]
• switchToHttp() assigns getRequest(), getResponse(), and getNext() onto the same host and maps them to argument indexes 0, 1, and 2. [packages/core/helpers/execution-context-host.ts:50-56]
• switchToWs() assigns getClient() and getData() onto the same host for argument indexes 0 and 1; getPattern() reads the final element of the current argument array. [packages/core/helpers/execution-context-host.ts:58-64]
• The switch methods use Object.assign(this, ...); therefore, each call has the side effect of adding or replacing those accessor methods on the existing instance rather than creating a separate adapter object. [packages/core/helpers/execution-context-host.ts:43-64]
• The class contains no explicit runtime validation, bounds checks, or thrown errors for the argument array, indexes, class reference, handler reference, or context type. [packages/core/helpers/execution-context-host.ts:13-64]

Core code creates this host for guards with the invocation arguments, instance.constructor, and callback, then sets the optional guard context type before passing the host to each guard’s canActivate. [packages/core/guards/guards-consumer.ts:18-22] [packages/core/guards/guards-consumer.ts:37-46] Shared context helpers also construct it from invocation arguments and optionally set its type for custom parameter factories. [packages/core/helpers/context-utils.ts:77-85] [packages/core/helpers/context-utils.ts:87-97]

Relationships

• IMPORTS → ExecutionContext
• IMPORTS → Type
• IMPORTS → ContextType
• IMPORTS → HttpArgumentsHost
• IMPORTS → RpcArgumentsHost
• IMPORTS → WsArgumentsHost

Used by

5 references from 5 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

Imported by (5)

• RpcHandlerMetadata — packages/microservices/context/rpc-context-creator.ts:35
• RpcProxy — packages/microservices/context/rpc-proxy.ts:6
• ListenersController — packages/microservices/listeners-controller.ts:45
• WsHandlerMetadata — packages/websockets/context/ws-context-creator.ts:34
• WsProxy — packages/websockets/context/ws-proxy.ts:6