Add Day_5: 面向对象(二) 继承复刻models.Model

Day_5/参考解答.py

@@ -0,0 +1,67 @@
+# -*- coding: utf-8 -*-
+"""
+Day_5 参考解答
+=============
+主题：面向对象（二）—— 继承。
+建议：先自己写，写不出来再看；看完后关掉文件自己默写一遍。
+"""
+
+import time
+
+class BaseModel:
+    objects = []            # 类属性：模拟数据库表（所有子类共用）
+
+    def save(self):
+        BaseModel.objects.append(self)
+        print(f"[DB] 已保存 {type(self).__name__}: {self}")
+
+    def delete(self):
+        BaseModel.objects.remove(self)
+        print(f"[DB] 已删除 {self}")
+
+    def to_dict(self):
+        return dict(self.__dict__)           # 实例的所有属性 => 字典
+
+    def __str__(self):
+        return f"<{type(self).__name__}#{id(self)}>"
+
+
+class Article(BaseModel):
+    def __init__(self, title, content, author):
+        self.title = title
+        self.content = content
+        self.author = author
+        self.created_at = time.strftime("%Y-%m-%d %H:%M:%S")
+
+    # 进阶：重写 save，先打日志，再调用父类逻辑
+    def save(self):
+        print(f"[LOG] 正在保存文章《{self.title}》...")
+        super().save()                       # 父类的 save 负责真正"入库"
+
+    def __str__(self):
+        return f"<Article: {self.title}>"
+
+
+class Comment(BaseModel):
+    def __init__(self, content, author):
+        self.content = content
+        self.author = author
+
+    def __str__(self):
+        return f"<Comment: {self.content[:10]}...>"
+
+
+if __name__ == '__main__':
+    a1 = Article("Django 入门", "从 Hello World 开始", "zhangsan")
+    a1.save()                                # 触发重写后的 save（带日志 + super）
+    c1 = Comment("写得太好了！", "lisi")
+    c1.save()
+
+    for obj in BaseModel.objects:
+        print(obj.to_dict())
+
+    print(issubclass(Article, BaseModel))    # True
+    print(isinstance(a1, BaseModel))         # True
+
+    a1.delete()
+    print(len(BaseModel.objects))            # 1（只剩评论）