Question

我有一个派生自包含自己的成员变量的基类的类。为了保持封装的类中的所有内容，我试图找出一种干净的方法来设置此成员变量，同时在同一方法中检索它。这是方法的样子（这是伪代码，可能不会编译）：

class Base
{
    virtual void MyVirtualMethod(double &output1, Object &output2)
    {
        // do base class stuff (does not set output1 because it does not need to)...
        output2 = whatever;
    }
}

class Derived
{
public:
    virtual void MyVirtualMethod(double &output1, Object &output2)
    {
        // do derived class stuff...

        m_DerivedMember = whatever;

        // do more stuff...

        output1 = m_DerivedMember;
        output2 = whatever2;
    }

private:
    double m_DerivedMember;
}

调用代码＃1

std::vector<DataPack> dataPack;

for each Base pointer...
{
    double output1(100); // some default value
    Object output2;
    base->MyVirtualMethod(output1, output2);

    dataPack.push_back(DataPack(output1, output2));
}

调用代码＃2

double output1(100); // some default value
Object output2;
base->MyVirtualMethod(output1, output2);

// do more stuff but does not actually use output1, just output2...

虽然这有效但对我来说似乎并不干净。我想我问自己一个更大的问题是，同时使用相同的方法作为getter和setter是一个好主意吗？谢谢！

Answer 1

虽然我不推荐这样做，但您可以返回对您的会员的引用，这样您就可以获得/设置操作。这就是std::vector重载operator[]的方式。类似的东西：

#include <iostream>
using namespace std;

class Foo
{
  int m_;
public:
  Foo(int m): m_(m){}
  int& get_set()
  {
     return m_;
  } 
  const int& get_set() const // for const-access
  {
     return m_;
  }
}; 

int main()
{
  Foo foo(10);
  cout << foo.get_set() << endl;
  foo.get_set() = 20;
  cout << foo.get_set() << endl;

  // that's why we need the `const` overload of `Foo::get_set`
  const Foo cfoo(100); 
  cout << cfoo.get_set() << endl;
}

Answer 2

要回答您的问题，单独的getter和setter是封装的核心。虽然它可以为您节省额外的功能，但它具有更加清晰和安全的功能，可以获得和设置单独的功能。这里有一些经过调整的代码可以更好地理解

class Derived : public Base
{
public:
    virtual void MyVirtualMethod(double &output1, Object &output2)
    {
        // do derived class stuff...

        m_DerivedMember = whatever;

        // do more stuff...

        output1 = m_DerivedMember;
        output2 = whatever2;
    }


/*
The setter
*/
void setDerivedMember(double m){
    m_DerivedMember = m;
}




/* 
the getter
*/

double getDerivedMember(){

    return m_DerivedMember;
}


private:
    double m_DerivedMember;
}

我们可以调用这些函数，如：

Derived d(1.5, string("I'm a string"));
d.setDerivedMember(5.00);
cout <<"Derived Member Value: " d.getDerivedMember()<<endl;

它会输出：

Derived Member Value: 5.00

希望有意义！

C ++ - 在同一方法中获取和设置成员变量？

2 个答案: