Importance of Solid Principles in Software Engineering and its examples in TypeScript

In software engineering, writing maintainable, scalable, and flexible code is crucial. It makes development easier, faster, and more efficient. However, as systems become more complex, it's easy for code to become messy and difficult to maintain and scale. Fortunately, SOLID principles in TypeScript offer a solution. 

In this blog, we will discuss the importance of SOLID principles in software engineering, SOLID principles code, and explore how to apply them in TypeScript to write clean, maintainable, and scalable code.

 

What are SOLID Principles?

First, let’s understand the Importance of SOLID principles in TypeScript and how SOLID principles make software designs simpler to comprehend!

Reducing dependencies allows engineers to alter one component of software without affecting others, which is the main objective of the SOLID principles. They are also meant to make designs simpler to comprehend, update, and expand. In the end, applying these design principles helps software engineers avoid problems and create flexible, efficient, and agile software.

What are SOLID Principles in Software Engineering? SOLID principles are a set of software design principles that guide developers on how to write maintainable, scalable, and flexible code. They are:

 

S: Single-responsibility Principle

To understand what are SOLID principles better, you need to know that the single-responsibility concept is a key aspect of it, which states that a class should only be accountable for one activity and one change-related reason. It becomes easier to implement single responsibility principle as it helps in maintaining the code's modularity and reusability. The same thing goes for modules and functions as well. There are many other benefits of single responsibility principle.

Here is an example of single responsibility principle:

class Company {

  public createEmployeeAccount(){

    // write logic

  }

 

  public generateEmployeeSalary(){

    // write logic

  }

 

  public calculateEmployeeLeave(){

    // write logic

  }

}

 

In the Company class mentioned above, you see an example of violating the single-responsibility principle and how to fix it in TypeScript. Since the concept of a single duty is violated, we ought to categorize the Company class into several degrees of responsibility. The concept of responsibility, according to SOLID, is a justification for change.

We observe in the company class that it tries to complete three tasks at once, which is incorrect. As an alternative, we might divide this obligation into three groups like in the given below:
 

class EmployeeAccount {

  public createEmployeeAccount(){

    // write logic

  }

}

 

class EmployeeSalary {

  public generateEmployeeSalary(){

    // write logic

  }

}

 

class EmployeeLeave {

  public calculateEmployeeLeave(){

    // write logic

  }

}

 

Now that the classes are separated, each has just one obligation, one responsibility, and just one change that needs to be made. Our code is now easier to understand and explain.

 

O: Open Closed Principles

Now let’s move to what is open closed principle!

Software entities should be open for extension but closed for modification, in accordance with the open-closed paradigm. Let’s look at the open-closed principle and how it helps in extending the codebase in TypeScript.

To know how to implement open-closed principle, write a code that follows this principle:

class Programmer{

      writing(){

        return "I can writing Code"

        }

 

 

      debug(){

        return "I can debug code"

        }

}

 

class TechLead extends Programmer {

      review() {

        return "I can review programmers code"

        }

}

 

 

const techLead = new TechLead();

 

 

console.log(techLead.debug());

 

I can share a scenario like your code that is already running in the production environment. After a few days, your client wants to add something to the existing features. So how to fit codebase with new requirements using Open Closed Principles? In that case, Open Close principles have come to solve this issue by extending the existing class and fit with new requirements.

 

L: Liskov Substitution Principle

Let’s move on to how to apply Liskov Substitution Principle in TypeScript! According to this rule, classes in software should be interchangeable as long as they both implement the same interface. No further adjustments should be needed after replacing the class, and the program ought to function as it did at first.

 

Example of Liskov substitution principle are given below:

class Programmer{

    write(){

        return "I can write code"

    }

    debug(){

        return "I can debug the code"

    }

}

interface SuperInterface{

    deploy():string

}

class SeniorProgrammer extends Programmer implements SuperInterface {

 

    deploy() {

      return "I can deploy my code to AWS"

    }

}

class SeniorArchitect implements SuperInterface{

    deploy()  {

        return "I can deploy my code to GCP"

    }

}

const seniorArchitect = new SeniorArchitect();

console.log(seniorArchitect.deploy());

 

Suppose you want to reuse a particular thing in different modules so that you can create a common interface for it and implement it in different classes based on your needs.

 

I: Interface segregation Principle

Let’s look at what is Interface segregation principle! According to this approach, we should divide very large interfaces (general-purpose interfaces) into smaller, more focused ones (many client-specific interfaces), so that clients only need to be aware of the methods that are relevant to them. Here’s an example of interface segregation principle.

 

class Programmer{

    drive(){

       return "I can write code"

    }

}

interface SuperInterface{

     problemSolving():string

}

interface SpeedyInterface{

     hyperSpeed():string

}

class SeniorProgrammer extends Programmer implements SuperInterface,SpeedyInterface {

    problemSolving() {

        return "I am very good in logical problem solving"

    }

    hyperSpeed()  {

        return "My typing speed is super fast"

    }

}

const seniorProgrammer= new SeniorProgrammer();

console.log(seniorProgrammer.hyperSpeed());

 

In Interface segregation principles, we can split a large interface into multiple ones for reducing redundant use cases. Suppose in an interface we define two functions and want to implement them in two different classes. But you saw that one class needs to implement two functions but another class needs only one function. So we should not define two functions in the same interface. We can segregate it into two interfaces. That’s the main theme of interface segregation principles.

 

D: Dependency inversion Principle

Let’s look at how to implement Dependency Inversion!

According to the idea of the Principle using Dependency Injection in TypeScript, entities should rely on abstractions (interfaces) rather than concretion (classes). Suppose you want to inject a whole class into another class to use it. In that case, dependency injection has come to solve this problem.

Here’s a more accurate representation for understanding Dependency Inversion Principle and Dependency Injection in Object-Oriented Programming.

 

class Programmer{

    write(){

        return "I can write code"

    }

}

interface SuperInterface {

    problemSolver():string;

}

interface SpeedyInterface {

    hyperSpeed():string;

}

 

class SuperProgrammer extends Programmer implements SuperInterface, SpeedyInterface {

    problemSolver()  {

        return "I am a good problem solver";

    }

    hyperSpeed()  {

        return "My typing speed is very fast";

    }

}

class WorldClassProgrammer {

    private programmer: SuperProgrammer;

    constructor(programmer: SuperProgrammer){

        this.programmer = programmer;

}

beginWithHighSpeed(){

 return `${this.programmer. hyperSpeed()} but can't do it for long run`;

}

}

const superProgrammer = new SuperProgrammer();

const worldClassProgrammer = new WorldClassProgrammer(superProgrammer);

console.log(worldClassProgrammer.beginWithHighSpeed());

 

Benefits of Using SOLID Principles

   By following SOLID principles and using Object-Oriented Programming, developers can create maintainable, scalable, and flexible code. Here are some ways how Object-Oriented Programming benefits from using SOLID Principles:

• Reduced code complexity: SOLID principles help to break down complex code into smaller, more manageable pieces.
• Improved code quality: SOLID principles help to create code that is easy to read, understand, and maintain.
• Improved testability: SOLID principles help to create code that is easy to test, reducing the likelihood of bugs and errors.
• Enhanced flexibility: SOLID principles help to create code that can be easily modified and extended.

 

Tips for Successful SOLID Principle Implementation

Here are some SOLID principles implementation tips:

• Start small: Don't try to apply all SOLID principles at once. Start with one principle and work your way up.
• Practice makes perfect: Applying SOLID principles takes practice. Keep practicing until it becomes second nature.
• Collaborate: Work with other developers to learn from their experiences and gain new perspectives.
• Keep it simple: Don't overcomplicate things. Keep your code simple and easy to understand.

Be sure to follow these best practices for implementing SOLID principles in software development to gain the best results. 

 

Conclusion

Systems that have been developed using SOLID design principles are more scalable, tested, maintainable, and reusable. Engineers around the world employ these ideas in the contemporary context. Therefore, it's crucial to apply these concepts in order to write decent code and use design principles that are competitive and adhere to industry standards