Module 4 introduces fundamental concepts in object-oriented programming (OOP) within TypeScript: interfaces and classes. These building blocks enable you to organize code effectively, promote code reusability, and improve maintainability.
4.1 Interfaces:
- Defining Contracts: Interfaces act as blueprints that specify the structure of an object, outlining the properties and methods it must have, but not their implementation.
- Syntax:
TypeScript
interface User {
name: string;
age: number;
greet(): string;
}
- Benefits:
- Improved code clarity: Interfaces document the expected structure of objects, making code easier to understand and maintain.
- Enhanced type safety: TypeScript enforces compatibility between objects and their corresponding interfaces, preventing type errors.
- Increased code reusability: Interfaces serve as contracts that can be implemented by multiple classes, promoting code reusability and flexibility.
4.2 Implementing Interfaces:
- Classes: Classes are blueprints for creating objects, defining their properties (data) and methods (functions).
- Implementing an interface: A class can implement one or more interfaces, signifying that it adheres to the specified contract.
- Syntax:
TypeScript
class Person implements User {
name: string;
age: number;
constructor(name: string, age: number) {
this.name = name;
this.age = age;
}
greet(): string {
return "Hello, my name is " + this.name + "!";
}
}
let alice = new Person("Alice", 30);
console.log(alice.greet()); // Output: Hello, my name is Alice!
4.3 Access Modifiers:
public: Properties and methods are accessible from anywhere in the code.private: Properties and methods are only accessible within the class itself.protected: Properties and methods are accessible within the class and its subclasses.
4.4 Inheritance:
- Building upon existing classes: Classes can inherit properties and methods from parent classes, promoting code reuse and extensibility.
- Syntax:
TypeScript
class Employee extends Person {
jobTitle: string;
constructor(name: string, age: number, jobTitle: string) {
super(name, age); // Call the parent class constructor
this.jobTitle = jobTitle;
}
getSalary(): number {
// Implement employee-specific logic for calculating salary
}
}
4.5 Practice and Challenges:
- Engage in coding exercises to define interfaces, create classes that implement them, and explore inheritance relationships.
- Practice using access modifiers to control access to properties and methods.
- Solve coding challenges that involve designing classes and their interactions using interfaces and inheritance, promoting code organization and reusability.
4.6 Conclusion:
By understanding interfaces and classes, you gain the ability to structure your TypeScript code in an object-oriented manner. Interfaces provide contracts for code clarity and type safety, while classes encapsulate data and behavior, promoting modularity and code reusability. This module equips you with essential tools to design well-organized and maintainable TypeScript applications.