The Singleton design pattern is a creational design pattern that ensures the existence of only one instance of a class throughout the application. It provides a global point of access to this instance, allowing other objects to use it consistently. The Singleton pattern is often used when you need a single, shared instance of a class that can be accessed from multiple parts of the application.
In the Singleton pattern, the structure itself is responsible for managing its own instance. It typically provides a static method, property or global variable that allows other objects to retrieve the singleton instance. The first time getter function or constructor is called, it creates the singleton object, and subsequent calls returns the same instance.
%%{init: {'flowchart': {'curve': 'stepAfter'}}}%%
flowchart LR
L[Logger]
D[Repository Layer]
S[Service Layer]
C[Controller Layer]
D <-->|Same Instance| L
S <-->|Same Instance| L
C <-->|Same Instance| L
When you need a global point of access to a single instance of a class, the Singleton pattern provides a convenient solution. It ensures that all objects within the application access the same instance, facilitating data sharing and coordination.
If you have a limited resource that needs to be shared, such as a database connection, file system, or thread pool, the Singleton pattern can be used to manage and control access to that resource. It guarantees that only stance of the resource is created and shared across the application.
Singleton can be used to store and access configuration settings that need to be shared and accessed from different parts of the application. It ensures that the settings are consistent and available globally.
Singleton can be used for centralized logging or caching mechanisms. A single instance can manage the logging or caching operations, ensuring consistency and avoiding conflicts.