避免调用成员变量的构造函数 [英] Avoid calling constructor of member variable

问题描述

我很确定这个问题已经被问过了。但即使搜索了几分钟，我没有找到任何可以回答我的问题的职位。我有以下C ++ - 类：

I'm pretty sure that this question has already been asked. But even after searching for some minutes, I didn't find any post which could answer my question. I have the following C++-class:

// Header-File
class A
{
    public:
    A();

    private:
    B m_B;
    C m_C;
};

// cpp-File
A::A()
: m_B(1)
{
    m_B.doSomething();
    m_B.doMore();
    m_C = C(m_B.getSomeValue());
}

现在我想避免 c $ c> A 调用 C m_C 的任何构造函数。因为在 A :: A（）的最后一行，我无论如何都要初始化 m_C 需要首先准备 m_B 。我可以为 class B 提供一个空的默认构造函数。但是这不是想法。

I now would like to avoid the class A to call any constructor of C m_C. Because on the last line in A::A(), I'm anyways going to initialize m_C myself because I need to prepare m_B first. I could provide an empty default constructor for class B. But that's not the idea.

我已经尝试将 m_C（NULL）添加到init- A :: A（）。有时它工作，有时它说没有构造函数以 NULL 作为参数。

I have already tried to add m_C(NULL) to the init-list of A::A(). Sometimes it worked, sometimes it said there was no constructor taking NULL as an argument.

m_C 左未初始化？我知道使用指针， m_C（NULL） -way工程。我不想使用 new 动态分配它。

So how can I have m_C left uninitialized? I know that with pointers, the m_C(NULL)-way works. And I don't want to allocate it dynamically using new.

任何想法都是值得赞赏的。

Any idea is appreciated.

推荐答案

您要求的是禁止的 - 正确的。这确保每个成员都被正确初始化。

What you ask is forbidden - and correctly so. This ensures that every member is correctly initialized. Do not try to work around it - try to structure your classes that they work with it.

想法：

• C有一个无效的构造函数


• C具有使该类可用的初始化方法


• 它已经被正确初始化或没有初始化，如果没有初始化就返回适当的错误。

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