改善程序设计技术的50个有效做法

改善程序设计技术的 50 个有效做法第二版 2002.3 Scott Meyers 侯捷译

[object Object],[object Object],[object Object],[object Object]

C++ 新标准新的类型 bool ,[object Object],[object Object],[object Object],[object Object]

新的转型动作 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

1. 尽量以 const 和 inline 取代 #define ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

＃ define ratio 1.653 // 编译器看不见 ratio ，只看见 1.653 // 一旦出错，不会报告 ,[object Object],[object Object],[object Object]

In Class 常量 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

2. 尽量以 <iostream> 取代 <stdio.h> ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

3. 尽量以 new 和 delete 取代 malloc 和 free ,[object Object],[object Object],[object Object],[object Object],[object Object]

4. 尽量使用 C++ 风格的注释形式 ,[object Object],[object Object],[object Object],[object Object],[object Object]

内存管理 (memory management) ,[object Object],[object Object],[object Object],[object Object]

5. 使用相同形式的 new 和 delete ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

typedef string addresslines[4]; ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

6. 记得在析构函数中以 delete 对付指针成员 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object]

7. 为内存不足的状况预作准备 ,[object Object],[object Object],[object Object],[object Object],[object Object]

typedef void (* new_handle )( ); ,[object Object],[object Object],[object Object],[object Object],[object Object]

可以自定义新的 new_handler 函数，用 set_new_handler 确认。 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

设计 new_handler 函数，令其完成如下任务： ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

C++ 不支持 class 中专用的 new_handler ，但仍可以在一个 class 中重载 operator new, 和 set_new_handler 函数，让它调用特定的 new_handler 函数，而不用系统给出的全局 new_handler 。 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

void *X:: operator new (size_t size) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

// 应用 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

可以做一个混合风格基类允许 “设定 class 专属 new_handler” ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

template<class T> ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

template<class T> ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

new_handler NewHandlerSupport<T> ::currentHandler; // 初始化为 0 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

8. 撰写 operator new 和 operator delete 时应遵守的公约 ,[object Object],[object Object],[object Object]

//new 函数的伪码 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

无穷循环可以让更多的内存可用，或安装一个不同的 new_handler ，或卸载 new_handler ，或抛出一个异常，或直接结束程序。

operator new 可以被继承，但要小心 , 否则会导致问题 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

改进的办法： ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

重写 operator delete ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

//member 版 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

9. 避免覆盖 new 的正规形式 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object]

10. 如果写了一个 operator new 不要忘记写一个 operator delete ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Airplane *p=new Airplane; // 要求内存不大 ,[object Object],[object Object],pa ,[object Object],Airplane 对象所需的内存纪录内存大小的数据

定制内存管理。 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

定义一个 memory pool 类，使每一个 pool 对象都是一个内存配置器。 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

构造函数、析构函数和赋值运算符 ,[object Object],[object Object]

11. class 内有成员指针并动态配置内存时，一定要有拷贝构造函数，赋值运算符重载

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],Hello World a b data data

12 构造函数中尽量以初始化代替赋值 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

有一种例外：一个类内有大量数据成员时，赋值比初始化效率高。 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

12. 数据成员初始化的次序应该和类内声明的次序相同 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

14. 总是让基类拥有虚析构函数 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

15. 让 operator= 返回 *this 的引用 reference ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

16. 在 operator= 中为所有的数据成员赋值 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

在 operator= 中检查是否“自己赋值给自己” ,[object Object],[object Object],[object Object],[object Object]

类和函数的设计和申明 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

18 ．努力让接口完满（ complete ）且最小化 ,[object Object],[object Object],[object Object]

19 ．区分成员函数、非成员函数和友元函数 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

20 ．避免将数据成员设置为公有数据 ,[object Object],[object Object]

21 ．尽可能使用 const ,[object Object],[object Object],[object Object],[object Object],[object Object]

函数中 const 可以修饰传回值，参数，成员函数时甚至可以修饰整个函数。 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

22 ．尽量使用引用参数传址 pass by reference ,[object Object],[object Object],[object Object],[object Object]

23 ．当你必须传回 objebct( 传值 ) 时不要传址 ( 引用） ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],& 错误。返回值地址指向局部对象，与局部对象同名，运算执行完毕，局部对象被析构，返回值指向一个不存在的地址。

24 ．函数重载和参数缺省之间，谨慎抉择 ,[object Object],[object Object],[object Object]

25 ．避免对指针类型和数值类型进行重载 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

26 ．防备隐性二义性状态 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

27 ．如果不想使用编译器暗自产生的成员函数，明确地拒绝 ,[object Object],[object Object],[object Object]

28 ．尝试切割 global namespace ( 全局命名空间 ) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

有三种方法取用 namespace 内的名字。 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

类与函数的实现 29 ．避免传回内部数据的 handles ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

31 ．千万不要返回“函数内局部对象的 reference” 或“函数内以 new 获得的指针所指的对象” ,[object Object],[object Object],[object Object],[object Object],[object Object]

32. 尽可能延缓变量定义式的出现 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

33 ．明智地运用 inline ,[object Object],[object Object],[object Object],[object Object]

34 ．将文件之间的编译关系降到最低 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

继承关系与面向对象设计 ,[object Object],[object Object],[object Object],[object Object],[object Object]

35 ．公有继承， “ isa” 的关系 ,[object Object],[object Object],[object Object]

36 ．区分接口继承（ interface inheritance ）和实现继承（ implementation inheritance ） ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

37. 绝对不要重新定义继承而来的非虚函数 ,[object Object],[object Object],[object Object]

38 ．绝对不要重新定义继承而来的缺省参数值 ,[object Object],[object Object],[object Object],[object Object],[object Object]

39 ．避免在继承中做向下转型（ castdown ）动作 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

40 ．通过 layering 技术来模塑 has-a 或 is-implemented-in-terms-of 的关系 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

41 ．区分继承和模板 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

42 ．明智地运用私有继承 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

43 ．明智地运用多继承 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

44 ．说出你的意思并了解你所说的每一句话 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

杂项讨论 45 ．清楚知道 C++ 编译器为我们完成和调用哪些函数 ,[object Object],[object Object]

46 ．宁愿编译和连接时出错，也不要执行时出错 ,[object Object],[object Object],[object Object],[object Object]

47 ．使用 non-local static objects 之前确定它已有初值 ,[object Object],[object Object],[object Object],[object Object],[object Object]

49 ．尽量让自己熟息 C++ 标准程序库 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

50 ．加强自己对 C++ 的了解

改善程序设计技术的50个有效做法

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