Flutter Design Patterns
Singleton, Factory, Repository, Dependency Injection, Service Locator, SOLID principles
1What is the Singleton pattern in Dart/Flutter?
What is the Singleton pattern in Dart/Flutter?
回答
Singleton ensures a class has only one instance and provides a global access point to it. In Dart, it's typically implemented with a factory constructor and a private static instance. This pattern is useful for shared services like configurations or API clients.
2How to correctly implement a Singleton in Dart using a factory constructor?
How to correctly implement a Singleton in Dart using a factory constructor?
回答
The standard implementation uses a private static _instance, a private _internal() constructor, and a factory constructor that always returns _instance. This approach ensures only one instance exists and is thread-safe in Dart thanks to the single-threaded event loop.
3What is the main disadvantage of the Singleton pattern in a Flutter application?
What is the main disadvantage of the Singleton pattern in a Flutter application?
回答
Singleton creates global state that makes unit testing difficult because it's hard to mock or replace the instance. It also introduces tight coupling between classes and can hide actual dependencies, making code less maintainable and harder to refactor.
What is the Factory pattern in object-oriented programming?
What is the difference between Factory Method and Abstract Factory in Flutter?
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