Singleton is a design pattern and is one of the simplest ones. It is useful in the cases when we want only a single instance of any object in our application. In this tutorial we will learn about the singleton pattern in Dart and how we can create a singletons in Dart. So let's get started
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What is singleton?
- One of the simplest design pattern
- There can only be one instance of the Class
- Class itself is responsible to keep track of its sole instance
- The instance is globally accessible through static method
- Constructor is private so it cannot be instantiated
When to use singleton?
- Mostly useful when multiple instantiation is costly in terms of configurations required
- Also useful when we want to access same object over and over across our app
- Lazy construction
- Singleton class shouldn’t require any params
- Should be thread safe Dart is a single threaded language
Creating singleton class in dart
Create a class and then follow the steps to make it a singleton pattern.
1. Make constructor private
2. Create instance variable
Create a private static instance variable, that keeps track of the sole instance.
3. Static getter
Finally, create a static getter method, that allows access of the instance globally. It is responsible to create the new instance if it's not previously created.