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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