Choosing Between Singleton and Prototype Scopes in Software Design

In which scenario, you will use singleton and prototype scope?

In software design, particularly in the context of dependency injection and object-oriented programming, the choice between singleton and prototype scopes depends on the specific requirements of your application. Here’s a breakdown of scenarios where each scope is appropriate:

Singleton Scope

Definition: A singleton scope ensures that a class has only one instance throughout the application lifecycle. This instance is shared across all requests and components.

Use Cases:

1. Shared Resources: When you have a resource that is expensive to create and should be shared across the application, such as a database connection pool, configuration settings, or logging services.

2. Global State: When you need to maintain a global state or configuration that should be consistent across different parts of the application, such as application settings or user sessions.

3. Performance Optimization: When instantiating an object is resource-intensive, and you want to avoid the overhead of creating multiple instances.

4. Centralized Control: When you want to control access to a resource or service from a single point, such as a service that manages access to a third-party API.

Prototype Scope

Definition: A prototype scope creates a new instance of a class every time it is requested. Each request for the prototype results in a new object.

Use Cases:

1. Stateful Objects: When you need a new instance of an object that maintains its own state, such as user sessions, form data, or temporary data that should not be shared.

2. Complex Object Creation: When the object requires complex initialization or configuration that varies with each request, such as different parameters for each instance.

3. Thread Safety: When you need to ensure that each thread or request has its own instance of an object to avoid concurrency issues.

4. Testing and Isolation: When you want to ensure that tests do not interfere with each other by using fresh instances of objects for each test case.

Summary

• Use Singleton Scope when you need a single, shared instance of a class that is expensive to create or represents a global state.
• Use Prototype Scope when you need a new instance of a class for each request, especially when the instances maintain their own state or require unique configurations.

Choosing the right scope is crucial for managing resources effectively and ensuring the correct behavior of your application.