> For the complete documentation index, see [llms.txt](https://wirebox.ortusbooks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wirebox.ortusbooks.com/advanced-topics/child-injectors.md).

# Child Injectors

## Overview

![](https://content.gitbook.com/content/MtgLfPeIR8KWTwoO8bDr/blobs/J7E823wV92E6Xnu8B3aX/image.png)

Welcome to the world of hierarchical dependency injection. We had the ability before to add a parent injector to WireBox, but you can not only add a parent, but also many children to the hierarchy.

Every injector has the capability to store an ordered collection (`ordered struct`) of child injectors via the `childInjectors` property. Child injectors are used internally in many instances to provide a hierarchical approach to DI where instances can be **searched** for locally, in the parent and in the children.

### Child Injector Methods

Here are some of the new methods to assist with child injectors:

* `hasChildInjector( name )` - Verify if a child injector has been registered
* `registerChildInjector( name, child )` - Register a child injector by name
* `removeChildInjector( name )` - Remove a child injector by name
* `getChildInjector( name )` - Get a child injector by name
* `getChildInjectors()` - Get all the child injectors registered
* `getChildInjectorNames()` - Get an array of all the registered child injectors

### Child Enhanced Methods

* `getInstance()`
  * The `getInstance()`method has an `injector` argument so you can **EXPLICITLY** request an instance from a child injector by name `getInstance( name : "service", injector : "childInjector" )`
  * Apart from the explicit lookup it can also do implicit hierarchical lookups using the following order:
    * Locally
    * Parent
    * All Children (in order of registration)
* `containsInstance( name )` - This method now also searches in the child collection for the specific `name` instance. The lookup searches in the following order:
  1. Locally
  2. Parent
  3. Children (in order of registration)
* `shutdown()` - The shutdown method has been enhanced to issue shutdown method calls to all child injectors registered.

### Getting Instances From Specific Child Injectors

The `getInstance()` has been modified to have an `injector` argument that you can use to specifically ask for an instance from that child injector. If the child injector has not been registered you will get a `InvalidChildInjector` Exception.

```javascript
getInstance( name: "CategoryService", injector : "ChildInjector" )
```

### Child Injector Explicit DSL

The following is the DSL you can use to **explicitly** target a child injector for a dependency. You will prefix it with `wirebox:child:{name}` and the name of the injector:

```javascript
// Use the property name as the instance name
property name="categoryService" inject="wirebox:child:childInjector"
// Use a specific instance name
property name="categoryService" inject="wirebox:child:childInjector:CategoryService"
// Use any DSL
property name="categoryService" inject="wirebox:child:childInjector:{DSL}"
```

####


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://wirebox.ortusbooks.com/advanced-topics/child-injectors.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.