C++ 重载解析 [英] C++ overload resolution

问题描述

鉴于下面的例子，为什么我必须显式使用语句 b->A::DoSomething() 而不仅仅是 b->DoSomething()>?

Given the following example, why do I have to explicitly use the statement b->A::DoSomething() rather than just b->DoSomething()?

编译器的重载决议不应该弄清楚我说的是哪种方法吗?

Shouldn't the compiler's overload resolution figure out which method I'm talking about?

我使用的是 Microsoft VS 2005.(注意:在这种情况下使用 virtual 没有帮助.)

I'm using Microsoft VS 2005. (Note: using virtual doesn't help in this case.)

class A
{
  public:
    int DoSomething() {return 0;};
};

class B : public A
{
  public:
    int DoSomething(int x) {return 1;};
};

int main()
{
  B* b = new B();
  b->A::DoSomething();    //Why this?
  //b->DoSomething();    //Why not this? (Gives compiler error.)
  delete b;
  return 0;
}

推荐答案

这两个重载"不在同一个范围内.默认情况下，编译器只考虑最小可能的名称范围，直到找到名称匹配.参数匹配在之后完成.在您的情况下，这意味着编译器会看到 B::DoSomething.然后它尝试匹配参数列表，但失败了.

The two "overloads" aren't in the same scope. By default, the compiler only considers the smallest possible name scope until it finds a name match. Argument matching is done afterwards. In your case this means that the compiler sees B::DoSomething. It then tries to match the argument list, which fails.

一种解决方案是将重载从 A 下拉到 B 的作用域:

One solution would be to pull down the overload from A into B's scope:

class B : public A {
public:
    using A::DoSomething;
    // …
}

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