blocks|key|180205|text|不，您不能直接从初始化器列表初始化基类成员。这是因为初始化顺序是以这种方式进行的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|180206|C%2B%2B标准n3337+§+12.6.2/10|offset|length|style|BOLD|180207|180208|在非委托构造函数中，初始化按以下顺序进行：|blockquote|180209|180210|-首先，并且仅对于最派生类(1.8)的构造函数，虚拟基类按照它们在基类的有向无环图的深度优先从左向右遍历时出现的顺序进行初始化，其中“从左到右”是基类在派生类基说明符列表中的出现顺序。|180211|-然后，直接基类按照在-specifier-list中出现的声明顺序被初始化(不管mem-initializers的顺序如何)。|180212|-然后，非静态数据成员按照它们在类定义中声明的顺序被初始化(同样，不管mem-initializers的顺序)。|180213|-最后，构造函数体的复合语句被执行。|180214|注意:声明顺序是为了确保基对象和成员子对象以与初始化相反的顺序被销毁。-结束注释|180215|180216|因此，您可以在基类中指定构造函数(它可以受到保护)，并在派生类初始化列表(should+be+preferred)中使用该构造函数，或者可以在派生类函数主体中分配给基类成员(不同的行为，不同的效果，效率也较低-您正在分配给默认的初始化(已有值)成员)。|180217|在前一种情况下，你可以这样写：|180218|struct+A+{
++++float+m_x;
++++float+m_z;
++++A(){}
protected:
++++A(float+x):+m_x(x)+{}
};

class+B+:+public+A+{
public:
++++B(float+z)+:+A(z)+{}
++++//+alternatively
++++//+B(float+z)+{
++++//+++++m_x+=+z;
++++//+}
};

int+main(){
++++B+b(1);
++++return+0;
}|code-block|syntax|javascript|180219|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/23493639/1141471^0|0|B|1|0|0|0|0|0|1|A|0|1|S|0|1|E|0|0|0|11|J|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1F|8|@$D|1G|E|1H|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|I|3|J|5|K|7|1J|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1L|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1M|8|@$D|1N|E|1O|F|G]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1P|8|@$D|1Q|E|1R|F|G]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1S|8|@$D|1T|E|1U|F|G]]|9|@]|A|$]]|$1|U|3|V|5|6|7|1V|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1W|8|@]|9|@]|A|$]]|$1|X|3|Y|5|6|7|1X|8|@]|9|@$D|1Y|E|1Z|1|20]]|A|$]]|$1|Z|3|10|5|6|7|21|8|@]|9|@]|A|$]]|$1|11|3|12|5|13|7|22|8|@]|9|@]|A|$14|15]]|$1|16|3|-4|5|6|7|23|8|@]|9|@]|A|$]]]|17|$18|$5|19|1A|1B|A|$1C|1D]]]]

No you cannot initialize base class members from initializer list directly. This is because order of initialization proceeds in this way

C++ Standard n3337 § 12.6.2/10

<blockquote>
 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). 
 
 — 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 ]
</blockquote>

So you can specify a constructor in a base class (it can be protected) and use that one in initialization list of derived class (<a href="https://stackoverflow.com/a/23493639/1141471">should be preferred</a>) or you can assign to a base class member in derived class ctor body (different behaviour, different effect and also less efficient - you are assigning to default initialized (already has value) member).

In the former case you might write it this way:

<pre><code>struct A {
 float m_x;
 float m_z;
 A(){}
protected:
 A(float x): m_x(x) {}
};

class B : public A {
public:
 B(float z) : A(z) {}
 // alternatively
 // B(float z) {
 // m_x = z;
 // }
};

int main(){
 B b(1);
 return 0;
}
</code></pre>

I'm having a hard time finding hits on google for this.

<pre><code>struct a {
 float m_x;
 float m_z;
public:
 a(float x): m_x(x) {}
};

class b : public a {
 b(float z): m_z(z) {}
};
</code></pre>

On clang 3.2:

<pre><code>error: member initializer 'm_z' does not name a non-static data member or base class
 b(float z): m_z(z) {}
</code></pre>

member initializer does not name a non-static data member or base class

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我很难在谷歌上找到这方面的搜索结果。struct a {    float m_x;    float m_z;public:    a(float x): m_x(x) {}};class b : public a {    b(float z): m_z(z) {}};在clang 3.2上：error: memb...

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