As a PHP developer, you may be familiar with the DI Container. An object in your application that controls how services (or objects) are instantiated is called a DI Container.
The majority of contemporary PHP frameworks, such as Symfony, Laravel, Yii, etc., are built around it. The fundamentals of PHP DI Container and its usage in PHP yii applications will be covered in this article.
Dependency Injection: What Is It?
Programming techniques such as dependency injection (DI) divide the creation and use of components. Object-oriented programming uses a design pattern that follows the SOLID principles (more specifically, the S and the D).
Other programming paradigms, like procedural or functional programming, also use similar concepts.
The phrase is made up of two keywords that aid in explaining the idea:
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Dependencies.
For many objects and services (dependencies) to function, code components need them.
There are various kinds of dependencies, like those on external resources, other items, or services.
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Injection.
In DI, dependencies are not created or linked internally by components.
Rather, the method introduces external dependencies (supplies).
This method distinguishes between dependencies and components.
Dependencies can take on many different forms. They are not a part of the component itself, but they are necessary for it to function.
Other components, such as databases, libraries, and APIs, can also function as dependencies.
The problem of dependency management is resolved by dependency injection. Dependency management is created and managed by an external source when dependency management is isolated from a component.
There are fewer connections between modules and components when separation (also known as decoupling) occurs. Reduced connections mean easier upkeep and more adaptability.
Code thus becomes reusable as a result of the components' independence and applicability in different scenarios. Teams can create modules concurrently and don't always need to coordinate.
Dependency Injection Container
An object that can instantiate, configure, and set up all of its dependent objects is called a dependency injection (DI) container.
Martin's post does a good job of outlining the benefits of DI containers. Here, we'll primarily go over how to use Yii's DI container.
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Dependency Injection
Via the class [[yii\di\Container]], Yii offers the DI container feature. The following types of dependency injection are supported by it:
- Constructor injection;
- Setter and property injection;
- PHP callable injection.
Constructor Injection
Type hints for constructor parameters enable constructor injection in the DI container. When the container is used to create a new object, the type hints inform it of which classes or interfaces are dependent.
Using the constructor, the container will attempt to obtain instances of the dependent classes or interfaces and then inject them into the new object.
Setter And Property Injection
Through configurations, setter and property injection are supported. You can supply a configuration when registering a dependency or creating a new object, and the container will use it to inject the dependencies through the appropriate setters or properties.
Php Callable Injection
In this instance, new instances of the class will be created by the container using a registered PHP callable. The callable is in charge of resolving dependencies and properly injecting them into the freshly made objects.
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How Is The Decorator Pattern For Improving Current Services Implemented Using Yii's Di Container?
A Decorator: What Is It?
An object that wraps another object and uses the same interface as the wrapped object is called a decorator. The decorator can add new logic before or after the delegation, and it can assign some or all of the methods to the wrapped object.
Additionally, the decorator can change the wrapped object's methods' parameters or return value. You can combine different decorators to create different combinations of behavior at runtime by using the decorator pattern.
How Do You Create A Decorator In Yii?
In Yii, you must define a class that implements the same interface as the service you wish to decorate in order to create a decorator.
For instance, you must implement the \yii\base\ResponseInterface in order to decorate the \yii\web\Response component. The original service must then be injected as a constructor dependency of the decorator class.
How Can A Decorator Be Registered In Yii's Di Container?
Yii's DI container requires the \Yii::$container->set() method in order to register a decorator there.
You can specify how a service should be configured and instantiated by the DI container using this method. As the second argument to this method, you can pass a callable, a configuration array, or the name of the class. In order to register a decorator, you must pass the original service as an argument to a callable that returns an instance of the decorator class.
In Yii, How Do You Apply A Decorator To A Service?
In Yii, the \Yii::$container->get() method is required in order to apply a decorator to a service. An instance of the service that the DI container has configured will be returned by this method.
The \Yii::$container->get() method will return an instance of the decorator class rather than the original service class if you have registered a decorator for the service.
How Do You Use Several Decorators In Yii For A Service?
You must register decorators in the order you want them to be applied if you want to use more than one for a given service in Yii.
The outermost decorator will be the last to register, and the innermost decorator will be the first to register. For instance, suppose you would like to use two decorators-one for adding cache control headers and the other for logging the response data-for the \yii\web\Response component.
Then, you will obtain an instance of the LoggingDecorator that wraps an instance of the CacheControlDecorator that wraps an instance of the original \yii\web\Response when you use the \Yii::$container->get() method.
Advantages of Putting in a DI Container
There are many advantages of using a DI container:
- Centralized configuration: The fact that all of your services are set up in one location facilitates management and modification.
- Dependency injection: The ability of DI Containers to inject dependencies into your services automatically simplifies the management of intricate dependencies.
- Lazy-loading: DI Container can minimize memory usage and increase performance by delaying the instantiation of services until they are required.
- Testing: DI Containers let you replace actual objects with mock objects, which simplifies the process of writing tests for your services.
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Disadvantages of Putting in a DI Container
The following are dependency injection's drawbacks:
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Complexity.
DI adds to the complexity of code when managing numerous dependencies or intricate configurations.
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Learning curve.
It takes time to understand the principles of DI fully and when to apply them.
The learning curve slows down the development of new projects.
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Overhead.
Smaller projects shouldn't use DI because it adds unnecessary overhead.
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Runtime errors.
Runtime errors arise from careless injection of dependencies.
It can be not easy to troubleshoot, particularly in complex environments.
Dependency Injection Types
Developers apply dependency injection in a variety of ways. Select the strategy that best fits the use case, programming language, and requirements.
An overview and sample of a few different dependency injection types are provided below.
Constructor Injection
One kind of dependency injection is constructor injection, which injects dependencies via a constructor. The constructor supplies the dependencies during the creation of an instance of a class or object.
Consequently, the class or object has all the dependencies it needs right away and runs correctly.
When a class or object needs dependencies in order to function, use constructor injection. A class or object instance can instantly access dependencies thanks to the injection of dependencies during class or object instantiation.
Setter Injection
Setter injection is a type of injection that uses setter methods or class properties to supply dependencies. After creating an object or class, the dependencies are manually updated by the developer.
When the setter methods are called, the object is consequently given the proper dependencies.
When a class or object operates without required dependencies, use setter injection. In this instance, the dependencies can be injected after runtime and are not required at instantiation.
With this method, dependencies can be dynamically changed after an object is created.
Method Injection
Dependencies are provided as method parameters via method injection, also known as parameter injection. When a method is called, dependencies are expected as arguments by the class or object.
For fine-grained dependency injection based on specific methods, use method injection. The greatest degree of decoupling is achieved by method injection, which is helpful when a class contains several methods that don't share the same dependencies.
Conclusion
In summary, managing the dependencies in your PHP application can be done effectively with the help of a DI Container.
You can manage intricate dependencies, centralize your service configuration, and enhance performance by utilizing a DI Container.
Paul is a highly skilled Full Stack Developer with a solid educational background that includes a Bachelor's degree in Computer Science and a Master's degree in Software Engineering, as well as a decade of hands-on experience. Certifications such as AWS Certified Solutions Architect, and Agile Scrum Master bolster his knowledge. Paul's excellent contributions to the software development industry have garnered him a slew of prizes and accolades, cementing his status as a top-tier professional. Aside from coding, he finds relief in her interests, which include hiking through beautiful landscapes, finding creative outlets through painting, and giving back to the community by participating in local tech education programmer.
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