问题描述
在初始化变量之前调用父类构造函数，还是编译器首先初始化该类的变量？
Are parent class constructors called before initializing variables, or will the compiler initialize the variables of the class first?
例如：
class parent {
protected:
int a;
public:
parent() : a(123) {};
};
class child : public parent {
int b;
public:
// question: is parent constructor done before init b?
child() : b(456), parent() {};
}
推荐答案
首先，只有最多
派生类（1.8）的构造函数，虚拟基类按照
的顺序初始化，它们出现在定向$ b的深度优先从左到右的遍历中$ b基类的非循环图，其中从左到右是在导出类
base-specifier-list中基类的外观的
的顺序。
— 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.
- 然后，直接基类在
声明顺序中初始化，因为它们出现在base-specifier-list
存储器初始化器）。
— 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).
- 然后，非静态
数据成员按照它们在
类定义中声明的顺序进行初始化（同样不考虑
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).
- 最后，执行
构造函数体的复合语句。
— Finally, the compound-statement of the constructor body is executed.
这篇关于在初始化变量之前是否调用父类构造函数？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！