const Declaration

[Clackdor]

How do I make use of the declaration 'const' if the variable is declared in a header file?

 

resource.h

class cPlayer {

public:    //stuff

private:  //other stuff

   float const movespeed;

}

Can't do this because I get a compiler error 'structure Player with uninitialized const members'

 

class cPlayer {

public:    //stuff

private:  //other stuff

   float const movespeed=4;

}

Can't give it a value in a .h

 

The code really works fine without the const, but some best practices I've been reading indicate it is a better idea for variables not affected by code to be declared as const being better for debugging than using #define or variables without const.

[Canardia]

Class initializers are compiled into the code, so they don't use CPU cycles:

#include <cstdio>

class Player
{       // autoprotected stuff
       const double movespeed, turnspeed;
       public:
       Player();
       const double& GetSpeed() const;
};

Player::Player():               // note the doublepoint to start the class initializer list
movespeed(4),           // this is a class initializer
turnspeed(2)                    // this also
{
}

const double& Player::GetSpeed() const
{
       return movespeed;
}

int main()
{
       Player player;
       printf("player.movespeed = %f\n", player.GetSpeed() );
}

Class initializers can be also used to call the parent classes constructor, this is very useful when you need to initialize the parent class with specific values too.

[Clackdor]

I am still getting.

 

error: structure 'Player' with uninitialized const members

 

in .h file

class cPlayer {

public:

   void LoadPlayer();
   void UpdatePlayer();

private:

   const float movespeed;

 

 

in .cpp file

void cPlayer::LoadPlayer():

movespeed(4)

{
// stuff
}

[Canardia]

Class initializers must be in the constructor (Player::Player()).

[Roland]

class cPlayer 
{

public: 
cPlayer() : movespeed(12) {}

private:
   const float movespeed ;

};

[Canardia]

It's bad to put code into the class declaration, Roland

[Clackdor]

Thanks Guys!

[TheoLogic]

@Clackdor; small remark. I see you have a LoadPlayer and no constructor. You need at minimum a constructor, and even if you work with a Load/Init/... function this should be private and called from the constructor. This is rather a design remark and the idea is pretty simple:

"If I create an object of your defined type, I expect it to be correctly initialized. I don't want to create + call a Load/Init/... function."

 

By the way, in C++11 there is a new feature called "Non-static data member initialization". This means you can set the default value in the header file like you did in the first post.