条款24：若所有参数皆需类型转换，请为此采用 non-member 函数

1.针对隐式转换的情况，可能会出现误用的情况

• 示例代码

#include <iostream>

class Rational
{
public:
    Rational(float iNum1 = 1, float iNum2 = 2) { fNum = iNum1 / iNum2; }
    ~Rational() {}
    //自定义逻辑
    const Rational operator * (const Rational& rhs) const{ return Rational(this->fNum, rhs.fNum);}

public:
    float fNum;
};

int main()
{
    Rational R1(1.0);
    Rational R2 = R1 * 2.0;
    Rational R3 = 3.0 * R2;
}

不符合类的设计逻辑

书中解释

2.解决：使用非成员函数来解决以上的问题

• 示例代码

#include <iostream>

class Rational
{
public:
    Rational(float iNum1 = 1, float iNum2 = 2) { fNum = iNum1 / iNum2; }
    ~Rational() {}

public:
    float fNum;
};

const Rational operator * (const Rational& r1, const Rational& r2)
{
    return Rational(r1.fNum, r2.fNum);
}

int main()
{
    Rational R1(1.0);
    Rational R2 = R1 * 2.0;
    Rational R3 = 3.0 * R2;
    std::cout << "end...................." << std::endl;
}