How do you use ZF's factories to create and inject dependencies with complex logic or parameters?

1 Service manager basics

The service manager is the central component of ZF's dependency injection system. It is a container that stores and retrieves services, which are any objects that provide some functionality to your application. You can configure the service manager to create services on demand, or to share them across the application. You can also use aliases, delegators, and initializers to customize the services.

2 Abstract factories

An abstract factory is a special type of service that can create multiple services based on a pattern or a convention. For example, you can use an abstract factory to create services that depend on a configuration array, or that implement a common interface. To use an abstract factory, you need to implement the AbstractFactoryInterface and register it with the service manager. The abstract factory will be invoked whenever the service manager cannot find a matching service.

3 Factory classes

A factory class is a more specific way to create a service. It is a class that implements the FactoryInterface and defines a createService method that returns an instance of the service. You can use a factory class to create services that require complex logic or parameters, such as database connections, mailers, or loggers. To use a factory class, you need to map the service name to the factory class name in the service manager configuration.

4 Injecting dependencies

Once you have created your services using factories, you need to inject them into the classes that depend on them. There are two main ways to do this: constructor injection and setter injection. Constructor injection is when you pass the dependencies as arguments to the constructor of the class. Setter injection is when you use setter methods to assign the dependencies to the class properties. Both methods have advantages and disadvantages, depending on your use case and preference.

5 Testing with dependency injection

One of the benefits of using dependency injection is that it makes your code easier to test. You can use mock objects or stubs to replace the real dependencies and isolate the behavior of the class under test. You can also use the service manager to override or replace the services in your test environment. For example, you can use a mock database adapter instead of a real one, or a null logger instead of a file logger.

6 Best practices

To get the most out of ZF's factories and dependency injection, here are some best practices to follow. First, use interfaces and type hints to define and enforce the contracts between your services and classes. Second, avoid using the service locator pattern, which is when you access the service manager from within your classes. This creates hidden dependencies and reduces testability. Third, use meaningful and consistent names for your services and factories, and document them well.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?