If a developer wants a clear concept for developing software in a proper & strategic way then they must follow SOLD principles. The SOLID principle is a coding standard and a design pattern which developers should try to follow to avoid a bad design. Also, Magento developers should follow this time-tested OOD (object-oriented design) principles make their code more resilient & more easily extended. When the developer builds a software following the bad design, the code can become more brittle, inflexible, small changes in the software can result in bugs. So, for these reasons, every Magento developer should follow SOLID principles promoted by Robert C Martin in order to make their code more logical, extendable, and easier to read.
What are the SOLID principles?
It is a set of principles for object-oriented design named as an acronym for five design principles that should be followed by Magento developers and other software developers to make software designs more flexible, understandable, and maintainable.
These SOLID Principles are as follows:
- Single Responsibility Principle (SRP)
- Open/Closed Principle (OCP)
- Liskov Substitution Principle (LSP)
- Interface Segregation Principle (ISP)
- Dependency Inversion Principle (DIP)
Why should Magento Developer Practice SOLID Principles?
Utilizing SOLID principles bring Magento developers with immensely gratifying results such as:
- Maintaining top coding standards.
- Making code that is scalable and repairable.
- Makes the code universally understandable.
Let’s have an in-depth look at these principles and understand why Magento developers should follow these standards:
Single Responsibility Principle
The principle states that there should never be more than one reason for a class to change. A class should contain only one responsibility. Following this principle makes the class more maintainable and can be easily modified. When a particular class serves multiple purposes or responsibility then it should be defined as a new class.
The example in Magento
\Magento\Framework\Event\Manager–Responsible for dispatching the events.
\Magento\Framework\Data\Form\FormKey\Validator–Responsible for validating the form key.
When Magento developers write a class, make it responsible for only one action to achieve a robust and manageable code.
The OCP principle specifies that software entities like (classes, modules, functions,etc.) should be open for extension but closed for modification. The ‘’open” part says that Magento developers can extend existing functionality. On the other hand “Closed” part states once a module has been developed and tested, the code should only be adjusted to correct bugs. If Magento developers could follow this principle strictly then it is possible to modify the behavior of the code without touching a piece of original code.
An example in Magento
\Magento\Framework\App\RouterInterface – To add any router.
And add the same to the RouterList(in di.xml). So, there no modification made to the existing code even though the router is added.
Liskov Substitution Principle
Another important SOLID principle is Liskov Substitution which states that “objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program”. According to object-oriented programming, When class B extends Class A, Class B can be a substitute for Class A. LSP extends the same fundamental principle, with a significant change – Class B Should be a substitute of Class A.
In the case of extending any Magento-native classes, Magento developers should follow the same structure. If anyone intend to remove any method or modify its parameters, then it will be against this principle. This may cause the application to break or generate unexpected results.
Interface Segregation Principle
A Client should not be forced to implement an interface that it doesn’t use.
This rule means that when one class depends upon another, the number of members in the interface that is visible to the dependent class should be minimized. Similar to the single responsibility principle, the aim of this principle is to minimize the side consequences and repetition by dividing the software into different, independent parts.
Examples in Magento
\Magento\Framework\View\Element\BlockInterface – implemented in all the blocks for rendering HTML content.
\Magento\Framework\DataObject\IdentityInterface – may implement in blocks or models for caching purposes.
For example, the Magento Core Team has combined both and can have only the BlockInterface. However, by doing so, all blocks are forced to have the cache methods that they might not use and will be a strict violation of the principle.
Dependency Inversion Principle
DIP principle makes two statements. One is that the high-level modules should not depend on low-level modules. Both should depend on abstractions. The second one is abstractions should not depend on the details. Details should depend upon abstractions.
Examples in Magento
Refer any native classes where they mostly inject the interfaces into the constructor instead of the implementation class to create the respective objects. Even when using the factory, it is recommended to create the factory for the interface.
These are the five simple and most commonly used object-oriented design principles that should be used & implemented by every Magento developer. Magento developers are strongly encouraged by Magento to utilize these SOLID principles effectively whenever needed. So, in the future, when any developer codes a new feature or modifies an existing one, keep these principles in mind to achieve the higher quality and maintainability in their code.