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How can I access varibles in a parent class?
Say I have CHILD_CLASS inside of PARENT_CLASS.
An I want a function in my CHILD_CLASS to access a varible in PARENT_CLASS.
How would I do that without saving that varible in a global to accessed externally?
>How can I access varibles in a parent class?
The "correct" object-oriented way would be to provide a protected member function for accessing the variable that the child class can inherit.
>Say I have CHILD_CLASS inside of PARENT_CLASS.
Are you talking about an inheritance hierarchy or nesting? If it's the former then see my answer above. If it's the latter, make the "child" class a friend of the "parent" class and reconsider your terminology. ;)
Yes, I am refering to "inheritance hierarchy".
>> The "correct" object-oriented way would be to provide
>> a protected member function for accessing the
>> variable that the child class can inherit.
:o I don't understand.
Code:class parent
{
private:
int d;
protected:
virtual int get_d( void ) // prob doesn't need to virtual
{
return d;
}
public:
parent() : d( 42 ){}
};
class child : public parent
{
private:
int x;
public:
child() : x(0){}
void whatever()
{
cout<< "Here's parent::d - " << get_d();
}
};
int main( void )
{
child df;
df.whatever();
}
But what I had the exact same class in a class?
>But what I had the exact same class in a class?
Why don't you show us what you have? I'm getting mixed signals.
Then read Prelude's reply. All you have to do is implement a protected function in the parent class which returns the value of the variable you desire. Then call this function from the child class and you're done.
I think he means something like:
going from his previous thread. SHow us what you got though.Code:class thing
{
thing *variable;
};
This is what I have so far.Code:class minimax
{
public:
minimax *ply;
char board[9];
int depth;
void look_ahead();
};
void minimax::look_ahead()
{
}
minimax my_ai;
I trying to make my child minimax class (ply) to make it's depth varible the same as it's parent's plus 1.
>I think he means something like:
Then it's not a problem. You can access the private members of an object of the same class, whether it's a member itself or the argument to a function:
Code:class thing {
thing *p;
int i;
public:
void foo1()
{
p->i = 321; // Just fine
}
void foo2 ( const thing& t )
{
t.p->i = 123; // Also fine
}
};
>> I trying to make my child minimax class (ply) to make it's depth varible the same as it's parent's plus 1.
You gonna call the child the same as the parent? (I know this is don in real life, but I don't think it's ok in programming)
Okay, this script has my parent access my child. But I need the child to access the parent, not the other way round.Code:class minimax
{
public:
minimax();
minimax *ply;
char board[20];
int depth;
void override_depth(int);
void look_ahead();
};
minimax::minimax(){
depth = ply.depth + 1; }
void minimax::override_depth(int dna){
depth = dna; }
void minimax::look_ahead()
{
}
>> You gonna call the child the same as the parent? (I know
>> this is don in real life, but I don't think it's ok in programming)
If this is the case, then an external varible will be the only thing I can do, right?
Also, should I not be trying to make my own minimax class, and just download one off some site?
There is no child or parent, there is one class...Quote:
Originally Posted by twomers
> Okay, this script has my parent access my child.
I think we have a confusion of terms here. It looks like you don't mean parent, as in base class; you mean the owner of a pointer to an instance of the same class.
Can you just do:
?Code:ply->depth = this->depth+1;
Hmm, that locks my program up.
Are you sure that ply->depth is the "parent"s varible rather than "child"s?
>> There is no child or parent, there is one class...
I know that. But the OP was talking about inheritance, so I got confused about what he meant.
WORKS!!!Code:int minimax__depth = 0;
class minimax
{
public:
minimax();
minimax *ply;
char board[20];
int depth;
void look_ahead();
};
minimax::minimax(){
depth = minimax__depth;
minimax__depth++; }
void minimax::look_ahead()
{
}
But,
Prog locks up.Code:if(ply.depth == 0) Beep(2000,100);
if(ply.ply[0].depth == 1) Beep(2000,100);
Also, locks up.Code:if(ply.depth == 0) Beep(2000,100);
if(ply.ply[0].depth == 1) Beep(2000,100);
I'm guessing that (in the ply.ply[0].depth) it's not trying to access ply's ply. Just ply.
Renaming my lead ply to ply1 would fix that, but, not when I want to do this for an example:
ply.ply[0].ply[2].ply[1].ply[0].depth
What should I do now?
That doesn't make any sense. Since ply is a pointer,
should not compile.Code:if(ply.depth == 0) Beep(2000,100);
if(ply.ply[0].depth == 1) Beep(2000,100);
It does though.
I learned that a compiler will see *char_var the same as char_var[infinite].
>I learned that a compiler will see *char_var the same as char_var[infinite].
...
What is the compiler you are using?
ply is a pointer. To access its member you do ply->depth. Not ply.depth.
okay using ply.ply->depth compiles but still locks up.
Using Dev-C++.
>> I'm guessing that (in the ply.ply[0].depth) it's not trying to access ply's ply. Just ply.
This still remains true, how can I get around that?
You are not reading anyone replies. so... good luck with your program
>> You are not reading anyone replies. so... good luck with your program
What do you mean I'm not reading anyone replies!!!
I have tried your suggestions, and they DON'T WORK.
Okay, so ply is a POINTER. Got it.
Where does that leave me?
Actually, now that I think of it, I am probably going about this whole thing the wrong way.
Thanks for the help guys, sorry all it did was show me that I'm doing it wrong. :rolleyes: