Registry Pattern - Revolutionize Your Object Creation and Management in your applications
Published: 2023-04-07 11:14:42

The Registry pattern is a design pattern that provides a centralized location for managing and creating instances of objects. It is useful when you have multiple instances of related objects that need to be created and managed, and can simplify object creation and management by providing a single point of access for creating and retrieving instances of those objects.

In other way, a registry object maintains a collection of named objects and provides methods for registering and retrieving those objects. This can improve performance by allowing the system to reuse existing objects rather than creating new ones each time they are needed. It also makes it easy to add new types of objects to the system without modifying existing code.

**Learning Management System (LMS)**

Let's consider a Learning Management System (LMS) that needs to manage different types of courses, such as online courses, in-person courses, and hybrid courses. Each course type has its own set of properties and behavior, and we want to be able to create multiple instances of each course type.

Here's an example of how we can use the Registry pattern to manage the different course types:

Define a base Course class that defines the common properties and behavior of all course types:

``` typescript
class Course {
  name: string;
  description: string;

  constructor(name: string, description: string) {
    this.name = name;
    this.description = description;
  }

  enroll(student: Student) {
    // enroll the student in the course
  }

  cancelEnrollment(student: Student) {
    // cancel the student's enrollment in the course
  }
}


```

Define a subclass for each course type, and add any additional properties or behavior specific to that course type:

``` typescript
class OnlineCourse extends Course {
  url: string;

  constructor(name: string, description: string, url: string) {
    super(name, description);
    this.url = url;
  }

  start(): void {
    // start the online course
  }
}

class InPersonCourse extends Course {
  location: string;

  constructor(name: string, description: string, location: string) {
    super(name, description);
    this.location = location;
  }

  schedule(): void {
    // schedule the in-person course
  }
}

class HybridCourse extends Course {
  url: string;
  location: string;

  constructor(name: string, description: string, url: string, location: string) {
    super(name, description);
    this.url = url;
    this.location = location;
  }

  start(): void {
    // start the online portion of the hybrid course
  }

  schedule(): void {
    // schedule the in-person portion of the hybrid course
  }
}

``` 
Create a CourseRegistry object that will store instances of each course type:

``` typescript
interface CourseConstructor {
  new (...args: any[]): any;
}

class CourseRegistry {
  private courses: {[key: string]: CourseConstructor} = {};

  registerCourse(courseType: string, constructor: CourseConstructor): void {
    this.courses[courseType] = constructor;
  }

  createCourse(courseType: string, ...args: any[]): any {
    const CourseConstructor = this.courses[courseType];
    if (!CourseConstructor) {
      throw new Error(`Course type '${courseType}' not registered`);
    }
    return new CourseConstructor(...args);
  }
}

``` 
Register each course type with the CourseRegistry:

``` typescript

const courseRegistry = new CourseRegistry();
courseRegistry.registerCourse('online', OnlineCourse);
courseRegistry.registerCourse('in-person', InPersonCourse);
courseRegistry.registerCourse('hybrid', HybridCourse);


``` 
Create instances of each course type using the CourseRegistry:

``` typescript
const onlineCourse = courseRegistry.createCourse('online', 'Introduction to JavaScript', 'Learn JavaScript online', 'https://example.com/js');
const inPersonCourse = courseRegistry.createCourse('in-person', 'Advanced React', 'Learn advanced React techniques in person', 'New York');
const hybridCourse = courseRegistry.createCourse('hybrid', 'Full-stack Web Development', 'Learn full-stack web development', 'https://example.com/webdev', 'San Francisco');

``` 
**Benefits of using the Registry pattern**

**Centralized management of object creation:** The Registry pattern provides a centralized location for managing and creating instances of objects, which can simplify object creation and management.

**Flexibility and extensibility**: By using the Registry pattern, you can add new types of objects to the system without modifying existing code, making the system more flexible and extensible.

**Improved performance:** The Registry pattern can improve performance by allowing the system to reuse existing objects rather than creating new ones each time they are needed.

**Easy access to objects:** The Registry pattern provides a simple way to access objects throughout the system, making it easy to share objects between different parts of the system.

**Demerits of using the Registry pattern**

**Increased complexity:** The Registry pattern can introduce additional complexity to a system, particularly if it is not implemented properly or is used excessively.

**Dependencies**: The Registry pattern can introduce dependencies between objects and the Registry, which can make it more difficult to test and maintain the system.

**Potential for naming collisions**: The Registry pattern relies on unique names for objects, so there is a risk of naming collisions if multiple objects have the same name.

**Potential for misuse**: The Registry pattern can be misused if it is not implemented properly, leading to issues such as memory leaks, poor performance, and difficult-to-maintain code.

Overall, the Registry pattern can be a useful tool in certain situations, particularly when managing multiple instances of related objects. However, like any design pattern, it should be used judiciously and with careful consideration of its potential benefits and drawbacks.