关于c ++：派生类中具有相同名称但签名不同的函数

Function with same name but different signature in derived class

我有一个同名的函数，但在基类和派生类中具有不同的签名。当我试图在从派生类继承的另一个类中使用基类的函数时，我收到一个错误。请参见以下代码：

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class A
{
public:
void foo(string s){};
};

class B : public A
{
public:
int foo(int i){};
};

class C : public B
{
public:
void bar()
{
string s;
foo(s);
}
};

我从GCC编译器收到以下错误：

1	In member function `void C::bar()': no matching function for call to `C::foo(std::string&)' candidates are: int B::foo(int)

号

如果我将int foo(int i){};从类B中移除，或者将其从foo1中重命名，那么一切都会正常工作。

这有什么问题？

相关讨论

这是因为如果名称查找在您的一个基中找到一个名称，它就会停止。它不会在其他基地遥遥领先。B中的函数隐藏A中的函数。您必须在B的范围内重新声明A的函数，以便从B和C中可以看到这两个函数：

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class A
{
public:
void foo(string s){};
};

class B : public A
{
public:
int foo(int i){};
using A::foo;
};

class C : public B
{
public:
void bar()
{
string s;
foo(s);
}
};

编辑：标准给出的真实描述是(从10.2/2开始)：

The following steps define the result of name lookup in a class scope, C. First, every declaration for the
name in the class and in each of its base class sub-objects is considered. A member name f in one sub-
object B hides a member name f in a sub-object A if A is a base class sub-object of B. Any declarations
that are so hidden are eliminated from consideration. Each of these declarations that was introduced by a
using-declaration is considered to be from each sub-object of C that is of the type containing the declara-
tion designated by the using-declaration.96) If the resulting set of declarations are not all from sub-objects
of the same type, or the set has a nonstatic member and includes members from distinct sub-objects, there is
an ambiguity and the program is ill-formed. Otherwise that set is the result of the lookup.

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在另一个地方(就在上面)，它可以说：

For an id-expression [something like"foo"], name lookup begins in the class scope of this; for a qualified-id [something like"A::foo", A is a nested-name-specifier], name lookup begins in the scope of the nested-name-specifier. Name lookup takes place before access control (3.4, clause 11).

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([…]我说)。注意，这意味着即使您在B中的foo是私有的，在A中的foo仍然找不到(因为访问控制稍后发生)。