C++ 嵌套类 getter 和 setter 不起作用

Question

I'm making a pokemon battle code. Here are codes that I've made. First, I define Pokemon class.

(pokemon.h)

class Pokemon{ ... 
private:
    int hp;
public:
    int gethp();
    void sethp(int n); 
...}

(pokemon.cpp)

... 
int Pokemon::gethp(){return hp;}
void Pokemon::sethp(int n){hp = n;} 
...

Next, I define Trainer class. Trainer has a list of pokemons.

(trainer.h)

class Trainer: public Pokemon {
private:
    Pokemon pokemons[3];
...
public:
    Pokemon getpokemon(int n);
    void setpokemons(int n, int m, int i);
...

(trainer.cpp)

Pokemon Pikachu(..., 160, ...)               //Pikachu's hp is defined to be 160.
...
Pokemon makepokemon(int n) {        
    if (n == 1) { return Pikachu; }
....
}
Pokemon Trainer::getpokemon(int n) { return pokemons[n-1]; }
void Trainer::setpokemons(int n, int m, int i) {
    pokemons[0] = makepokemon(n);
    pokemons[1] = makepokemon(m);
    pokemons[2] = makepokemon(i);
}
...

Now, when I use gethp/sethp in the main fucntion, I have a problem.

(main part)

Trainer me;
me.setpokemons(1, ...);           // My first pokemon is pikachu then.

...

cout << me.getpokemon(1).gethp();             //This gives 160.
me.getpokemon(1).sethp(80);                   //I want to change Pikachu's hp into 80.
cout << me.getpokemon(1).gethp();             //Still this gives 160.

The problem is that sethp is not working. I guess that I need to use call by reference at some point to fix this, but I don't get how I should do.

How can I fix this problem?

Answer 1

me.getpokemon(1).sethp(80)

Let's walk through this--you're calling me.getpokemon(1) , which returns a copy of a Pokemon from me 's pokemons array. You then call sethp on the copy, setting its hp to 80. And then, since the copy isn't saved anywhere, you never see it again until it's destroyed...

What you want instead, is to cause getpokemon(1) to return a reference to the pokemons item insetad of a copy, so that when you call sethp() , you're modifying the original. You can do that by changing the function to return a reference instead of a copy:

Pokemon& Trainer::getpokemon(int n) { return pokemons[n-1]; }
//    ^^^