在头文件中定义const对象

Question

I have a question concerning the const keyword in C++. I have the following class:

Foot.h

class Foot
{
public:
   Foot (bool isRightFoot);
   const Vector internFootAxis;
   const Vector externFootAxis;
   bool isRightFoot;
private:
   Body* body;
}

Where Vector is a class implementing basic R^3 vector operations. internFootAxis denotes the vector which goes from the center of the foot (represented as a Body object - this is a class representing a physical object) to the big toe. externFootAxis denotes the vector which goes from the center of the foot to the little toe.

I want the initial value of internFootAxis and externFootAxis to be const (because I am applying operators at each iteration in the graphical display main loop to those vectors which change the inner state of the vector). Unfortunately, the values of internFootAxis(t=0) and externFootAxis(t=0) depends if I am considering the left or right foot, therefore I need to declare their values inside the constructor of Foot and not outside the class.

Technically I want to do the following

Foot.cpp

Foot::Foot(bool isRightFoot)
{
body = new Body();
     if (isRightFoot)
     {
         internFootAxis(1,1,0);
         externFootAxis(1,-1,0);
     }
     else
     {
         internFootAxis(1,-1,0);
         externFootAxis(1,1,0);
     }
}

Is there a simple way to do that ? Thanks a lot for your help

V.

Answer 1

Use initializer lists:

Foot::Foot(bool isRightFoot)
  : internFootAxis( 1, isRightFoot ? 1 : -1, 0)
  , externFootAxis( 1, isRightFoot ? -1 : 1, 0)
{
    body = new Body();
}