C++ 类成员初始化序列

Question

我知道在 class 中，成员按照列出的顺序进行初始化。这是否适用于将变量分组为 public 和 private 等？我的困惑是我无法弄清楚是否有偏好，例如 private 成员按照它们在 public 成员之前列出的顺序进行初始化，而不管私有(private)变量在哪里列出关于类声明中的公众(我知道对基类成员存在这种偏见)

Answer 1

类初始化的规则在[class.base.init]/11中有详细说明

In a non-delegating constructor, initialization proceeds in the following order:

• First, and only for the constructor of the most derived class (1.8), virtual base classes are initialized in the order they appear on a depth-first left-to-right traversal of the directed acyclic graph of base classes, where “left-to-right” is the order of appearance of the base classes in the derived class base-specifier-list.

• Then, direct base classes are initialized in declaration order as they appear in the base-specifier-list (regardless of the order of the mem-initializers).

• Then, non-static data members are initialized in the order they were declared in the class definition (again regardless of the order of the mem-initializers).

8 Finally, the compound-statement of the constructor body is executed.

[ Note: The declaration order is mandated to ensure that base and member subobjects are destroyed in the reverse order of initialization. —end note ]

^强调我的

因此，当我们查看项目符号 3 时，它明确指出成员是按照其在定义中出现的顺序构造的。这意味着无论 private、public 或它们在类成员初始化列表中的列出方式如何，它们都将按照声明的顺序构造。