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 dependencies 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 ...
• This component will not ...

4. Dependencies on Other Framework Components

• Zend_Exception
• ReflectionClass

5. Theory of Operation

The purpose of Zend_DI is to provide and easier way to test atomic units of code in isolation, and to mock dependencies which one component may refer to. Zend_DI minimizes coupling between groups of classes, makes unit testing much simpler, and provides an easy way to re-configure a library to use custom implementations of components.

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: Proposal accepted
• Milestone 3: Working release
• 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_Container_Registry
• Zend_DI_Container_Registry_Interface
• Zend_DI_Component_Factory
• Zend_DI_Component_Exception

8. Use Cases

• Foo.php

class Foo {
public function __construct(
FooInterface Component1 = null,
FooInterface Component2 = null,
arg1 = null,
arg2 = null) {
}
}

• Test.php

$di = new Zend_DI_Container();

// Define a class and create an instance
$di->loadClass('Foo')->newInstance();

// Example: Inject dependency
$di->loadClass('Foo')
->addDependency('Component1')
->newInstance();

// Example: Inject multiple dependencies
$di->loadClass('Foo')
->addDependencies('Component1' [, 'Component2' [, ...]])
->newInstance();

// Example: Pass arguments to the constructor
$di->loadClass('Foo')
->addDependency('Component1')
->addDependency('Component2')
->addArgument('arg1')
->addArgument('arg2')
->newInstance();

// Or...
$di->loadClass('Foo')
->addDependencies('Component1' [, 'Component2' [, ...]])
->addArguments('arg1' [, 'arg2' [, ...]])
->newInstance();

// Get an instance of the class
$obj = $di->getInstance('Foo');

9. Class Skeletons