在派生构造函数中访问基本成员时出现问题 [英] Problem accessing base member in derived constructor

问题描述

给定以下类：

class Foo
{
    struct BarBC
    {
    protected:
        BarBC(uint32_t aKey)
            : mKey(aKey)
              mOtherKey(0)

    public:
        const uint32_t mKey;
        const uint32_t mOtherKey;
    };


    struct Bar : public BarBC
    {
        Bar(uint32_t aKey, uint32_t aOtherKey)
            : BarBC(aKey),
              mOtherKey(aOtherKey) // Compile error here
    };
};

我在指示的点收到编译错误：

I am getting a compilation error at the point indicated:

error: class `Foo::Bar' does not have any field named `mOtherKey'.

任何人都可以解释一下吗？我怀疑这是一个语法问题，因为我的 Bar 类被定义在 Foo 类中，找到一个方法。

Can anyone explain this? I suspect it's a syntactical problem due to my Bar class being defined within the Foo class, but can't seem to find a way around it.

这是简单的公共继承，所以 mOtherKey 应该可以从 Bar 构造函数。是吗？

This is simple public inheritance, so mOtherKey should be accessible from the Bar constructor. Right?

或者是与 mOtherKey 是const并且我已经初始化它的事实 0 在 BarBC 构造函数中？

Or is it something to do with the fact that mOtherKey is const and I have already initialised it to 0 in the BarBC constructor?

推荐答案

您不能通过成员初始化器列表初始化基类的成员，只能通过类本身的直接和虚拟基类和非静态数据成员。

传递其他参数到基类的构造函数：

You can't initialize members of a base class through a member initializer list, only direct and virtual base classes and non-static data members of the class itself.
Pass additional parameters to the base class' constructor instead:

struct BarBC {
    BarBC(uint32_t aKey, uint32_t otherKey = 0)
      : mKey(aKey), mOtherKey(otherKey)
    {}
    // ...
};

struct Bar : public BarBC {
    Bar(uint32_t aKey, uint32_t aOtherKey)
      : BarBC(aKey, aOtherKey)
    {}
};

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