====================
Dependency Injection
====================

.. javadoc-import::
    com.dfsek.terra.api.Platform
    com.dfsek.terra.api.addon.BaseAddon
    com.dfsek.terra.api.inject.annotations.Inject

Terra uses a simple annotation-based dependency injection framework to provide instances of important API objects
to addons. The dependency injection framework reduces boilerplate by allowing addons to choose which objects they
need to have access to.

Injecting to a Field
====================

To inject to a field, simply make the field non-final and non-static, and annotate it :javadoc:`Inject`.

Example
-------

.. literalinclude:: code/dependency-injection.java
    :language: java

This example demonstrates injecting the :javadoc:`Platform` and :javadoc:`BaseAddon` instances. This is a very common
scenario, as both of these objects are required for :doc:`handling events<events>`

Injected Types
==============

The :javadoc:`Platform` instance is injected into all addons. Bootstrap addons may inject additional types into addons
they load. See the :ref:`di-in-entry-points` section for information about injected types in Manifest Addons.