设计模式练习

设计模式是软件工程中非常重要的概念，它可以帮助开发者写出更加可维护、可扩展和可复用的代码。以下是一些常见的设计模式及其简要说明：

• 单例模式（Singleton）：确保一个类只有一个实例，并提供一个全局访问点。
• 工厂模式（Factory Method）：定义一个用于创建对象的接口，让子类决定实例化哪一个类。
• 策略模式（Strategy）：定义一系列算法，将每个算法封装起来，并使它们可以互换。
• 观察者模式（Observer）：当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并自动更新。

设计模式

以下是一个简单的单例模式示例：

class Singleton:
    _instance = None

    @staticmethod
    def get_instance():
        if Singleton._instance is None:
            Singleton._instance = Singleton()
        return Singleton._instance

    def do_something(self):
        print("Doing something important...")

# 使用单例
singleton = Singleton.get_instance()
singleton.do_something()

更多关于设计模式的内容，请参考设计模式专题。

# Design Pattern Practice

Design patterns are a crucial concept in software engineering that helps developers write more maintainable, scalable, and reusable code. Here are some common design patterns and their brief descriptions:

- **Singleton Pattern**: Ensures that a class has only one instance and provides a global point of access.
- **Factory Method Pattern**: Defines an interface for creating objects, allowing subclasses to decide which class to instantiate.
- **Strategy Pattern**: Defines a family of algorithms, encapsulates each one, and makes them interchangeable.
- **Observer Pattern**: When an object's state changes, all objects that depend on it are notified and automatically updated.

![Design Patterns](https://cloud-image.ullrai.com/q/design_patterns/)

Here is a simple example of the Singleton pattern in Python:

```python
class Singleton:
    _instance = None

    @staticmethod
    def get_instance():
        if Singleton._instance is None:
            Singleton._instance = Singleton()
        return Singleton._instance

    def do_something(self):
        print("Doing something important...")

# Using Singleton
singleton = Singleton.get_instance()
singleton.do_something()

For more information about design patterns, please refer to the Design Patterns section.