Passing variables across classes with objects - class

Question

Alright so I've been continuing to learn about classes and oop languages. And am a bit confused.
If I was to have a separate class for player stats. And in that class I have some private ints and then some functions to change them publicly.
Say I want to change and get those ints From my main class. I make an object and assign them to local variables then I can call the local variables in my main script. Then update the variable in the stat class.
It seems a little silly that I have to make a local variable as well as a separate variable in a different class.
To me it would make sense to just be able to call the separate class in a new object whenever I wanted to access the variables in the stat class but I can't...
Let me know if this isn't clear as I can try to expand more.
Thanks
Ben

Answer 1

You do not have to make new variables in the "main" class ....
you can just use the getters and setters through the object that you created.
Also copying variables from player stats to main class is not a good idea because now you have to maintain two copies of same data, at least until you are in scope of main class. If not handled correctly it can also cause data inconsistencies.
Assuming you are using Java, you can do this.
public class PlayerStats{
private int var1=20;
public void setVar1(int var1){
this.var1=var1
}
public int getVar1(){
return var1
}
}
public class mainClass{
PlayerStats pStats = new PlayerStats();
pStats.getVar1();
pStats.setVar1(14);
System.out.println(pStats.getVar1());
}
Thanks for that answer definately cleared things up however, in the object created in mainClass if I create the object in one function how do I use it in another function in the same class?
Depends on how and if the two functions are connected and how central that object is to your class.
If the object is very central to class :
That is, you are using it almost in all the function, your class revolves around playing with that object, then you can create it at class level something along these lines
public class mainClass{
PlayerStats pStats = new PlayerStats();
public void function1() {
pStats.setVar1(14);
System.out.println(pStats.getVar1());
}
public void function2(int x) {
pStats.setVar1(x);
System.out.println(pStats.getVar1());
}
}
If two functions are not connected :
Just make a new object inside the function scope, if possible.
This is better than creating an object at class level, because the object becomes eligible for garbage collection after the function is finished executing. Whereas, the object created at class level stays in the memory as long as the object (instance of main class) is in the memory.
If two functions are connected, i.e you are calling one function from inside the second function :
you can just pass the object as an argument, something along these lines
public class mainClass{
public void function1() {
PlayerStats pStats = new PlayerStats();
pStats.setVar1(14);
function2(pStats)
}
public void function2(PlayerStats x) {
System.out.println(pStats.getVar1());
}
}
Also google dependency injection, it is an important concept, try to use it as often as possible. It produces good decoupled and testable design
There is so much more to say, people have written books on this topic, OO Design is an art in itself.