使用函数对象重构 C++ 代码

c++ code refactoring using function objects

本文关键字：C++ 代码 重构 对象 函数      更新时间：2023-10-16

我有一些功能，可以根据启动时（在构造函数中）设置的值返回值。由于这些条件值只设置一次，我不想一直检查它们。有没有办法只做一次if-check，然后不使用函数对象或其他机制一次又一次地做？

class MyValue {
    bool myVal; //set only once in the constructor
    int myval1; //often updates
    int myval2; //often updates

    myValue(bool val, int val1, int val2)
    {
        myVal = val; // only place where myVal is set
        // this value changes often in other functions not shown here
        myval1 = val1;
        // this value changes often in other functions not shown here
        myval2 = val2;
    }
    int GetMyValue() //often called
    {
        if(myval)    /* Is there a way I dont have to do an if check here? 
                        and simply write a return statement? */
            return myval1;
        return myval2;
    }    
};

使用指针：

class MyValue
{
   int* myVal;
   int myval1; //often updates
   int myval2; //often updates
  myValue(bool val, int val1, int val2)
  {
     if (val) { 
         myVal = &myval1; 
     } else { 
         myVal = &myval2 
     }
     myval1 = val1;
     myval2 = val2;
  }
  int GetMyValue() //often called
  {
     return *myval;
  }
};

（甚至更好的参考，如Rabbid76答案）

使用对myval1或myval2引用的成员，引用必须在构造函数中初始化一次：

class MyValue
{
    bool myVal; //set only once in the constructor
    int myval1; //often updates
    int myval2; //often updates
    int &valref;
public:
    MyValue( bool val, int val1, int val2 )
        : myVal( val )
        , myval1( val1 )
        , myval2( val2 )
        , valref( val ? myval1 : myval2 )
    {}
    int GetMyVal() { return valref; }
};
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