Under Construction This proposal is under construction and is not ready for review.

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Zend Framework: Zend_DI Component Proposal

Table of Contents

1. Overview

Zend_DI is a dependency injector component, similar in concept to PicoContainer, but smaller and easier to use. The architecture of the Zend_DI component is based on the following concepts:

• Dependency injection is a technique that consists of passing objects via the constructor or setter methods.
• The Container provides an easy way of re-configuring a package to use custom implementations of components.
• Responsibility for object management is taken over by whatever container is being used to manage those objects.

2. References

• Martin Fowler Dependency Injection pattern
• PicoContainer

3. Component Requirements, Constraints, and Acceptance Criteria

• This component will use Reflection.

4. Dependencies on Other Framework Components

• Zend_Config
• Zend_Exception
• Zend_Registry

5. Theory of Operation

Zend_DI minimizes coupling between groups of classes, makes unit testing much simpler, and provides an easy way to re-configure a package to use custom implementations of components. For example:

Once we separate configuration from use, we can easily test the Car with different engines. It's just a matter of re-configuring the package and injecting Zend_Car_Parts_Engine_Gas instead of Zend_Car_Parts_Engine_Fuel.

Zend_DI provides generic factory classes that instantiate instances of classes. These instances are then configured by the container, allowing construction logic to be reused on a broader level. Typically, responsibility for object management is taken over by whatever container is being used to manage those objects.

6. Milestones / Tasks

• Milestone 1: Proposal finished
• Milestone 2: Working release
• Milestone 3: Proposal accepted
• Milestone 4: Unit tests
• Milestone 5: Documentation
• Milestone 6: Future enhancements

7. Class Index

• Zend_DI_Container
• Zend_DI_Exception
• Zend_DI_Container_Manager
• Zend_DI_Container_Exception
• Zend_DI_Component_Factory
• Zend_DI_Component_Exception

8. Use Cases

Dependent class

Constructor Dependency Injection

The component handles injections via the constructor or setters methods. In addition, Zend_DI allows the user to map out specifications for components and their dependencies in a configuration file and generate the objects based on that specification. The configuration object can be set using the setConfig() method.

Containers

You can tell Zend_DI what classes to manage by adding them to a container (the order of registration has no significance):

Containers can be retrieved using the Zend_DI_Container_Manager::getContainer() method, which returns an instance of the Zend_Registry class.

9. Class Skeletons

• Zend_DI_Container