Maybe a stupid question

[yamaha]

Maybe this is a stupid beginners's question:

Inside my class I need to use a structure. This structure will be unique for each class instance. So, the point is: should I use a variable or a pointer ?


Thank you.

[eker676]

Everything inside a class will be unique for every class instance.
I would declare the structure as a normal variable. Unless C++ has some funny exceptions I haven't had the chance to experience using a normal variable structure should work.

[yamaha]

Ok, thank you. But - I'm comming from C - I need to malloc it, right ?

[eker676]

I'm pretty new myself. I have never had to use a structure inside a class so I don't know how to declare a new structure.
I will look around and try to find out but someone more experienced than myself will probably have to answer your last question.

EDIT: I'm not sure if this is what your looking for but here is a little example of using a structure inside a class.

#include <iostream>

using namespace std;

struct a_struct 
{
    int b;
};
        
class a_class
{
    public:
        a_struct something;

};

//To use it I would go like this

int main()
{
    a_class abc;
    abc.something.b = 10;
   
 
    cout << abc.something.b << endl;
    
    system("pause");
    return 0;
}

[yamaha]

I think I figured out with your help.

Suppose I have a structure called MyData. The following code:

class Test {
	MyData data;
public:
	Test()	{ data = (MyData *) malloc(sizeof(MyData)); }
}

is right or wrong ? Now I think it's wrong because data is not a pointer, so it doesn't need to be malloced because it already has the amount of memory allocated to it (the size of MyData).

This, to be right should be:

class Test {
	MyData *data;
public:
	Test()	{ data = (MyData *) malloc(sizeof(MyData)); }
}

I'm right about this ?

[kbw]

Your class can have an object as in MyData or a pointer as in MyData*.

If you are using a pointer, your should initialise and deinitialise with the constructor/descructor. You'll also need to define a copy consturctor and assignment operator as the defaults will just work on the pointers, not the objects pointed to.

The style you chose will depend on what you're doing.

class Test1
{
	MyData	data;

public:
	Test1()
	{
	}
};

class Test2
{
	MyData*	pdata;

public:
	Test2()
		:	pdata(new MyData)
	{
	}
	~Test2()
	{
		delete pdata;
	}
	Test2(const Test2 &n)
		:	pdata(new MyData)
	{
		*pdata = *n.pdata;
	}
	Test2& operator=(const Test2 &n)
	{
		if (this != &n)
		{
			*pdata = *n.pdata;
		}
		return *this;
	}
};

[yamaha]

Ok, I got it. Thank you guys for your support.