C ++游戏编程帮助。 超简单

Question

I am in a bit of a jam. I am building a game, and for some odd reason, I cannot call on variables from one class to another. it was only in this specific section of code in which it does not work, so any help is appreciated. Thanks in advance:

here's the code:

class HeadsUpDisplay
{
private:
    int frame;
public:
    SDL_Rect HealthBar[20];
    SDL_Rect offset;
    void init();
    void render();
}HUD;

void HeadsUpDisplay::init(){
    offset.x = SCREENW*.9;
    offset.y = SCREENH/10;
    HealthBar[0].x = 0;
    HealthBar[0].y = 0;
    HealthBar[0].w = 204;
    HealthBar[0].h = 14;

    HealthBar[1].x = 204*1;
    HealthBar[1].y = 0;
    HealthBar[1].w = 204;
    HealthBar[1].h = 14;

    HealthBar[2].x = 204*2;
    HealthBar[2].y = 0;
    HealthBar[2].w = 204;
    HealthBar[2].h = 14;

    HealthBar[3].x = 204*3;
    HealthBar[3].y = 0;
    HealthBar[3].w = 204;
    HealthBar[3].h = 14;

    HealthBar[4].x = 204*4;
    HealthBar[4].y = 0;
    HealthBar[4].w = 204;
    HealthBar[4].h = 14;

    HealthBar[5].x = 204*5;
    HealthBar[5].y = 0;
    HealthBar[5].w = 204;
    HealthBar[5].h = 14;

    HealthBar[6].x = 204*6;
    HealthBar[6].y = 0;
    HealthBar[6].w = 204;
    HealthBar[6].h = 14;

    HealthBar[7].x = 204*7;
    HealthBar[7].y = 0;
    HealthBar[7].w = 204;
    HealthBar[7].h = 14;

    HealthBar[8].x = 204*8;
    HealthBar[8].y = 0;
    HealthBar[8].w = 204;
    HealthBar[8].h = 14;

    HealthBar[9].x = 204*9;
    HealthBar[9].y = 0;
    HealthBar[9].w = 204;
    HealthBar[9].h = 14;

    HealthBar[10].x = 204*10;
    HealthBar[10].y = 0;
    HealthBar[10].w = 204;
    HealthBar[10].h = 14;

    HealthBar[11].x = 204*11;
    HealthBar[11].y = 0;
    HealthBar[11].w = 204;
    HealthBar[11].h = 14;

    HealthBar[12].x = 204*12;
    HealthBar[12].y = 0;
    HealthBar[12].w = 204;
    HealthBar[12].h = 14;

    HealthBar[13].x = 204*13;
    HealthBar[13].y = 0;
    HealthBar[13].w = 204;
    HealthBar[13].h = 14;

    HealthBar[14].x = 204*14;
    HealthBar[14].y = 0;
    HealthBar[14].w = 204;
    HealthBar[14].h = 14;

    HealthBar[15].x = 204*15;
    HealthBar[15].y = 0;
    HealthBar[15].w = 204;
    HealthBar[15].h = 14;

    HealthBar[16].x = 204*16;
    HealthBar[16].y = 0;
    HealthBar[16].w = 204;
    HealthBar[16].h = 14;

    HealthBar[17].x = 204*17;
    HealthBar[17].y = 0;
    HealthBar[17].w = 204;
    HealthBar[17].h = 14;

    HealthBar[18].x = 204*18;
    HealthBar[18].y = 0;
    HealthBar[18].w = 204;
    HealthBar[18].h = 14;

    HealthBar[19].x = 204*19;
    HealthBar[19].y = 0;
    HealthBar[19].w = 204;
    HealthBar[19].h = 14;

}

void HeadsUpDisplay::render(){


    if(character.characterhealth >95 && character.characterhealth <= 100)
    {
        frame = 19;
    }
    if(character.characterhealth >90 && character.characterhealth <=95)
    {
        frame = 18;
    }
    if(character.characterhealth >85 && character.characterhealth <= 90)
    {
        frame = 17;
    }
    if(character.characterhealth >80 && character.characterhealth <= 85)
    {
        frame = 16;
    }
    if(character.characterhealth >75 && character.characterhealth <= 80)
    {
        frame = 15;
    }
    if(character.characterhealth >70 && character.characterhealth <= 75)
    {
        frame = 14;
    }
    if(character.characterhealth >65 && character.characterhealth <= 70)
    {
        frame = 13;
    }
    if(character.characterhealth >60 && character.characterhealth <= 65)
    {
        frame = 12;
    }
    if(character.characterhealth >55 && character.characterhealth <= 60)
    {
        frame = 11;
    }
    if(character.characterhealth >50 && character.characterhealth <= 55)
    {
        frame = 10;
    }
    if(character.characterhealth >45 && character.characterhealth <= 50)
    {
        frame = 9;
    }
    if(character.characterhealth >40 && character.characterhealth <= 45)
    {
        frame = 8;
    }
    if(character.characterhealth >35 && character.characterhealth <= 40)
    {
        frame = 7;
    }
    if(character.characterhealth >30 && character.characterhealth <= 35)
    {
        frame = 6;
    }
    if(character.characterhealth >25 && character.characterhealth <= 30)
    {
        frame = 5;
    }
    if(character.characterhealth >20 && character.characterhealth <= 25)
    {
        frame = 4;
    }
    if(character.characterhealth >15 && character.characterhealth <= 20)
    {
        frame = 3;
    }
    if(character.characterhealth >10 && character.characterhealth <= 15)
    {
        frame = 2;
    }
    if(character.characterhealth >5 && character.characterhealth <= 10)
    {
        frame = 1;
    }
    if(character.characterhealth >0 && character.characterhealth <= 5)
    {
        frame = 0;
    }
    SDL_BlitSurface(health, &HealthBar[frame], screen, &offset);
}

so the problem is, in each if statement, I get the error "erro: 'character' was not declared in this scope"; I tried to prototype the class too, which did not solve the problem. I appreciate any help, even negative feedback, at least it is something.

Answer 1

YOur class does not have "character" field. See for yourself:

class HeadsUpDisplay
{
    private:
       int frame;
    public:
       SDL_Rect HealthBar[20];
       SDL_Rect offset;
       void init();
       void render();
};

You have frame , HealthBar and offset . Yet in every method you decalred you try to access "character".

character was an object from another class.

C++ class does not know that another object exists. To access another object, you should either pass it into method by reference or pointer:

void HUD::render(Character &character){
    if (character.whatever)
        ....
}

void HUD::render(Character *character){
    if (character->whatever)
        ....
}

Or it should be declared as global variable BEFORE function body that tries to access it.

Character character;//or extern Character character;

void HUD::render(){
    if (character.whatever)
        ....
}

If "character" wasn't mentioned in any form before compiler encounters function body that tries to access character, compiler won't know what "character" is.

It is generally a good idea to avoid using global variables when possible.