# callModuleInitHook

**Kind:** Function

**Source:** [`packages/core/hooks/on-module-init.hook.ts`](https://github.com/nestjs/nest/blob/master/packages/core/hooks/on-module-init.hook.ts#L37)

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

Calls the `onModuleInit` function on the module and its children
(providers / controllers).

`callModuleInitHook` runs the `onModuleInit()` lifecycle hook for a Nest module’s initialized controllers, providers, injectables, and middleware. It processes non-transient and transient instances before invoking the module class’s own hook when its dependency tree is static.

## Signature

```ts
async function callModuleInitHook(module: Module): Promise<void>
```

## Parameters

| Name | Type |
|---|---|
| `module` | `Module` |

**Returns:** `Promise<void>`

## Diagram

```mermaid
graph LR
  A[Module] --> B[Controllers]
  A --> C[Providers]
  A --> D[Injectables]
  A --> E[Middleware]

  B --> F[Invoke onModuleInit]
  C --> F
  D --> F
  E --> F

  F --> G[Non-transient instances]
  G --> H[Transient instances]
  H --> I[Module class onModuleInit]
```

## Usage

```ts
import { callModuleInitHook } from '@nestjs/core/hooks/on-module-init.hook';
import { Module } from '@nestjs/core/injector/module';

// Typically called internally by Nest during application initialization.
async function initializeModule(moduleRef: Module) {
  await callModuleInitHook(moduleRef);

  console.log('Module lifecycle hooks have completed.');
}
```

## AI Coding Instructions

- Treat this as an internal lifecycle utility; application code should usually implement `OnModuleInit` rather than call this function directly.
- Ensure providers, controllers, injectables, and middleware are fully instantiated before invoking module initialization hooks.
- Preserve the ordering: execute child instance hooks before the module class’s own `onModuleInit()` hook.
- Keep transient and non-transient instance handling separate so each lifecycle hook is invoked for the correct resolved instances.
- Only invoke the module class hook when its dependency tree is static and the class implements `onModuleInit()`.

## Relationships

- IMPORTS → `OnModuleInit`
- IMPORTS → `isFunction`
- IMPORTS → `isNil`