从书中复制的代码无法编译。已弃用或打字错误？

Question

这是一本免费的 c++ 电子书中的程序，但无法编译。起初我将它打出来，但意识到它无法编译后，我尝试从电子书中直接复制到代码块 13.12 中。它仍然无法编译。这本电子书是 2010 年的，所以可能代码不符合当前标准，或者某处存在语法错字。请帮我看看哪里出了问题。

错误是：

error: extra qualification 'Critter::' on member 'operator=' [-fpermissive]|

密码是：

#include <iostream>

using namespace std;


class Critter
{
public:
    Critter(const string& name = "", int age = 0);
    ~Critter(); //destructor prototype
    Critter(const Critter& c); //copy constructor prototype
    Critter& Critter::operator=(const Critter& c); 
op
    void Greet() const;

private:
    string* m_pName;
    int m_Age;
};

Critter::Critter(const string& name, int age)
{
    cout << "Constructor called\n";
    m_pName = new string(name);
    m_Age = age;
}

Critter::~Critter() //destructor definition
{
    cout << "Destructor called\n";
    delete m_pName;
}

Critter::Critter(const Critter& c) //copy constructor definition
{
    cout << "Copy Constructor called\n";
    m_pName = new string(*(c.m_pName));
    m_Age = c.m_Age;
}

Critter& Critter::operator=(const Critter& c) 
{
    cout << "Overloaded Assignment Operator called\n";
    if (this != &c)
    {
        delete m_pName;
        m_pName = new string(*(c.m_pName));
        m_Age = c.m_Age;
    }
    return *this;
}

void Critter::Greet() const
{
    cout << "I’m " << *m_pName << " and I’m " << m_Age << " years old.\n";
    cout << "&m_pName: " << cout << &m_pName << endl;
}

void testDestructor();
void testCopyConstructor(Critter aCopy);
void testAssignmentOp();

int main()
{
    testDestructor();
    cout << endl;

    Critter crit("Poochie", 5);
    crit.Greet();
    testCopyConstructor(crit);
    crit.Greet();
    cout << endl;

    testAssignmentOp();
    return 0;

}
void testDestructor()
{
    Critter toDestroy("Rover", 3);
    toDestroy.Greet();
}
void testCopyConstructor(Critter aCopy)
{
    aCopy.Greet();
}
void testAssignmentOp()
{
    Critter crit1("crit1", 7);
    Critter crit2("crit2", 9);
    crit1 = crit2;
    crit1.Greet();
    crit2.Greet();
    cout << endl;

    Critter crit3("crit", 11);
    crit3 = crit3;
    crit3.Greet();
}

Answer 1

如消息所说，

中多了一个Critter::

Critter& Critter::operator=(const Critter& c);

因为它在 class 声明中，所以它必须是 class 的成员并且不需要以 class 名称作为前缀。

Critter& operator=(const Critter& c);

是正确的形式。

class 名称前缀仅在成员定义在外部 class 时使用，如示例后面的代码。

Answer 2

从该运算符原型中删除 Critter::

从书中复制的代码无法编译。已弃用或打字错误？

Code copied from a book won't compile. Deprecated or typo?

c++

codeblocks