What is Magento 2 Dependency Injection?
Last Updated | May 15, 2023
What is Dependency Injection?
In order to understand Magento 2 dependency injection, we must first have a clear understanding of classes. A class could be considered as a blueprint of an object. It doesn’t exists itself, but has all the data needed to create such an object. A class states all the attributes that make up an object. For example, if a human is an object, the class will contain all the attributes exhibited by the human such as age, height, weight, and other data.
Now to understand dependency injections, if simply put, dependency is a relationship that is required by a class from another external source or class that the previous class requires to function correctly. The injection is a method that can pass that particular dependency relationship to the dependent class. For example, if I have a class X that fetches data using class Y, we can say that my class X is dependent on class Y.
Mind you that it is not the vice versa. One of the most iconic example to elaborate dependency injections was explained by John Munsch, who gave the idea of dependency by using a refrigerator and a kid. When the kid wants to get something from the refrigerator, they can get it themselves.
However, they may cause problems such as leaving the door open or looking for something that is no longer in the fridge. What the kid must do is to ask their mom or dad for what he/she needs. This means that the kid, who is a collaborating class, should rely on the other foundation classes, the parents, to achieve the desired results. This dependency injection in Magento is a win-win situation for users.
This is because the object is passed to the dependent class, instead of allowing the other dependent class to find the object or create one from scratch. For people who have no experience In PHP frameworks, it is quite difficult to elaborate it for them at such an advanced level so that they can make the dependency injection in Magento by themselves. In order to create such associations for novice users, it is best to hire Magento developers from a certified Magento web development company. They will be able to create and physically show you the changes in the live code as well.
What are the basics of Magento 2 Dependency Injection?
There are several basics of dependency injections in Magento 2 that need to be understood. If I have a class in Magento 2 that makes use of a Magento 2 helper class, can correctly state that my original class has a dependency on that Magento 2 helper object. An example for helper classes in real life can be explained using a scenario. If person A is constructing a house, they will begin with the design of the walls and the pillars.
But when it comes to the entry point of the house, you realize that you need a gate. So would you make it yourself or directly purchase from a vendor. Of course the latter is a more pragmatic approach. This is how a dependency class makes use of helper classes in Magento 2. This can decouple the original class from the construction of its dependent class. This is basically how the helper class is utilized in Magento 2.
Magento 2 utilizes the dependency injection to replace its original functionality that was first provided by the Mage class in Magento 1. x.
The dependency injection in Magento can also be used as a design pattern that can directly allow dependencies to be declared to external objects that then supply those dependencies. Generally, interfaces are used to declare dependencies, and then the dependencies are directed to another class that will provide the concrete implementation for the interfaces. This can be used for loose coupling of code because object A will no longer be responsible for generating its own dependencies.
It is object B that will decide the implementations on run time. This will in turn provide implementations to object A based on the desired behavior or different configurations for use as per scenario. This is an extremely important building block for basic because it helps extension developers in their work. This is because the dependency injection in Magento formulates the basis of how Magento produces its own classes.
Dependency inversion principle.
Another basic but important principle for dependency injection in Magento is to be aware of the dependency inversion principle. This principle makes use of abstractions/ interfaces/ virtual classes in your code to reduce the direct dependency in code. As a result, the high-level classes make use of the abstractions of the low-level classes instead of collaborating with them directly.
When abstract classes/ interfaces are used in the Magento code, it results in a decreased risk of incompatibility bugs when Magento changes the fundamental application framework for the interfaces. This ensures that the class can function accurately instead of worrying about how the class implements the functions. The Magento codebase follows the inversion principle. This results in users having mapping their own customized implementations of Magento abstract classes to other services using a dependent class or a di.xml file.
Compiling the dependencies.
Magento uses the code compiler tool that can collect all of the dependency information of classes and then store them in subsequent files. During the process of class generation, the object manager uses the information to instantiate concrete objects in the code. However, there are some service classes that do not exist in the codebase such as interceptors, proxies, and factories that can be declared in the configuration of code. These service classes can then be generated with the help of the compiler.
The Magento 2 platform makes use of the automatic dependency injection (ADI) which is then further derived to the constructor injections. In Magento 2, this means the passing of objects in the parameter of a constructor will aid the developer in following the rules for injection. The alternate to the Mage class method of Magento 1 is the dependency injection in Magento 2.
Magento dependencies have two major types as well. One is the injectable dependency and the other is the non-injectable dependency.
The newable type consists of objects for which injections are not possible. They can only be instantiated by creating a new class every time they are required. The objects that require external user inputs or data from databases, fall into this category of transient objects. Even if you try to inject these objects in the back0end code, you will receive an incorrect or incomplete object due to an error that will not let the object be instantiated.
For example, one cannot depend on a model object such as a product. This is because a product ID or an explicit request an empty or new instance will be needed. But since we will not be able to specify the data inside the signature of the constructor, Magento will not inject the object. In order to get around this limitation, only the injectable objects can depend on the library routines like factories that can produce non-injectable objects.
These injectable objects are obtained through dependency injection. They themselves are a singleton service object. The object manager uses the store’s configurations of the d.xml file to instantiate the objects and then inject them into constructor calls. The injectable objects can also depend on other injectable objects in the constructors. However, this is only possible when the dependency chain never circles back to the original object that is also injectable.
What Are the Different Types of Magento 2 Dependency Injection?
Dependency injections in Magento mean that the class will be able to use objects to perform different functions. The use of a parent class with the help of dependency injection can be used to reuse code. For example, a class of Customers that needs data from another class of Magento is conceived as one class is dependent on the other class for data or results. There are two major types of dependency injections in Magento 2. These dependency injections are known with multiple names such as constructor injection and a method injection. These are known as aggregation and composition relationships in software design and analysis.
The constructor injection is perhaps the most commonly used method to inject dependencies in Magento 2. In this dependency injection in Magento, the developer needs to add a parameter in the constructor class to inject a dependency. This should be the default choice for making dependencies because the injection addresses the most common and most simple scenarios where a class requires dependencies with one or more relationships.
In Magento 2, if current customer details are needed, then a dependency can be injected into the created class easily, there will be no need to write the complete code again to get the data of the customer. To understand this example in detail, an example will be discussed. Suppose there is a class consisting of a data block of customized modules to get the data of the customers and it also has a helper class dependency to get the customer name. A function will be used to call the logic of another class so separate codes do not need to be written to get the same result.
When your class makes use of a specific method in a particular scenario, the objects used are called the operational dependencies. If a single class is quite resource-consuming to instantiate, and considering the class will not be used regularly, you can consider using the service library of proxy. For required dependencies and optional dependencies of an object, it is critical to make use of the constructor dependency for optimal performance.
The method injection is the second type of dependency injection in Magento 2. This injection type passes the dependency as a parameter in the method or function of a certain class. The method injection is best utilized when the dependency is different on each function call of the same class. When objects need to perform certain actions for a dependency that is not possible to inject, it is preferable to make use of method injections.
The method injections also involve the passing of a method parameter to further use in class logic. When a certain method depends on a class, then we must pass the class as a dependency in our method. This example is best understood in the Magento event observer. If you want a further explanation for this type of injection, once you hire Magento developers for the store, they can show the functioning of the method injection live.
These injections define and use the interfaces that were declared for the dependency injections.
Why Magento 2 Dependency Injection is preferred over Object Manager?
The object manager is a manager of code used in larger applications, like Magento, that can avoid boilerplate code when objects are being composed while they are being instantiated. In Magento 2, the object manager interface acts as the object manager. Object managers have responsibilities such as creating objects in proxies and factories, instantiating parameters automatically inside the class constructors, and managing the dependencies by creating the preferred class once a constructor requests for its interface.
There are multiple usage rules for the object manager such as classes should not call for the object manager by themselves due to a constructor dependency. No direct calls to the object manager will be entertained as the Magento framework handles the manager independently. The direct use of functions will prevent the type validation.
The programmatic product updates may result in products being assigned to the wrong store views with the incorrect status because the access control list will contain incorrect scripts and settings. As a result, the product will fail to be validated and end up with incorrect assignments on stores with the wrong statuses.
If the create() function of the object manager is called so that objects for the classes can be created. It will then get and pass the value of the constructor parameter from the fi.xml files but it is absolutely not preferable to make use of the object manager. The object manager should not be used because it primarily defeats the original purpose of dependency injection in Magento.
No doubt it provides benefits by requiring less code to write, but it does not follow the development processes of Magento 2 and at times creates dependencies that are hidden and not needed in the first place. However, it is still used in the core of Magento 2 at some places but Adobe says they will get this refactored soon enough. So the best recommendation given our Magento Web Development Company is that do not make use of the object manager.
It is a good coding practice for the developers to be aware of what the code depends on, rather than having multiple hidden dependencies in the body of the code for no reason. This is why Magento users prefer dependency injections instead of object managers.
There are some exceptional cases where the object manager can be used in scenarios such as in static magic methods for wakeup () or sleep () etc. The object manager can be used to maintain a backwardly compatible relationship with the class constructor. It can be used in a global scope such as in integration tests. It is most preferable to hire Magento integration services from expert companies that ensure following the correct procedures so that such exceptional cases are not originated. The object manager can also be used as a dependency which will further be used for instantiating objects such as proxies or factories.
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These are multiple reasons why Folio3 is the best suited Magento Web development company for clients to hire. Folio3 also provides the most affordable Magento pricing packages for clients. We have offices all across the globe and you can visit us anytime for a meeting. If it is not feasible, you can always contact our service agents to book consultations or for any queries you may have.
The dependency injection is the best method to reduce tight coupling between the codebase and the application. This also enables to manage complexity and future changes in the code making it reusable. The Magento community also recommends making use of dependency injections in Magento 2 rather than using the object manager.
It is critical for developers to follow the coding patterns and coding standards while developing in Magento 2. Even though there are some exceptional cases where object managers can be used, it is best to not develop a habit as Adobe will refactor it soon anyway.
What are the types of dependency in Magento?
Magento dependencies have two major types as well. One is the injectable dependency and the other is the non-injectable dependency. The non-injectable dependencies can only be instantiated by creating a new class every time they are required. All the objects that require external user inputs or data from databases, fall into this category of transient objects. Even if you try to inject these objects in the backend code, you will receive an incorrect or incomplete object due to an error that will not let the object be instantiated.
In order to get around this limitation, only the injectable objects can depend on the library routines like factories that can produce non-injectable objects. The injectable objects are obtained through the dependency injection. They are singleton service objects. The injectable objects can also depend on other injectable objects in the constructors. However, this is only possible when the dependency chain never circles back to the original object that is also injectable.
What is Dependency Injection Magento?
The dependency injection in Magento is a relationship that is required by a class from another external source or class which the previous class requires to function correctly. The injection is a method that can pass that particular dependency relationship to the dependent class. For example, if I have a class X that fetches data using class Y, we can say that my class X is dependent on class Y. Mind you that it is not the vice versa. To access the data, it will make use of injections.
The two types of dependency injection in Magento are the constructor dependencies and the method dependencies. The constructor injection is perhaps the most commonly used method to inject dependencies in Magento 2. In this dependency injection in Magento, the developer needs to add a parameter in the constructor class to inject a dependency. The method injection is the second type of dependency injection in Magento 2. This injection type passes the dependency as a parameter in the method or function of a certain class. The method injection is best utilized when the dependency is different on each function call of the same class.
It is best to hire Magento developers when creating stores because creating dependencies requires coding skills and the logic of object-oriented programming.