simple class variables question

edpoole · #1 01-Jun-2005, 19:34

Hi there.

If I had a class with the following sorts of methods involving passing around other classes, is it better to keep the variables as pointers or just regular variables?

I mean, should I do something like this:

CPP / C++ / C Code:


class a {
public:
 Date getDate() { return date; }
 void setDate(Date d) { date = d; }
 Time getTime() { return time; }
 void setTime(Time t) { time = t; }
private:
 Time time;
 Date date;
};

or like this?

CPP / C++ / C Code:

class a {
public:
 a() {
   time = NULL;
   date = NULL;
  }
 ~a() {
   if(time != NULL) delete time;
   if(date != NULL) delete date;
  }
 Date* getDate() { return date; }
 void setDate(Date* d) {
   if(date != null) delete date;
   date = new Date();
   date.setDate(&d);
  }
 Time* getTime() { return time; }
 void setTime(Time* t) {
   if(time != null) delete time;
   time = new Time();
   time.setTime(&t);
  }
private:
 Time* time;
 Date* date;
};

Thanks.

Dave Sinkula · #2 01-Jun-2005, 20:41

I'm no expert, but I'll say this.

One of the reasons you want dynamic allocation is when you don't know how many objects you will need at runtime. So if your class a could have 7 times and 3 dates, that might be a good reason to choose it. If your class a is always going to have exactly 1 time and 1 date, then why bother? Perhaps if the times or dates are really large and/or contain stuff that may vary in size.

Generally, I'd go with the first. If you don't know how many class a's you will need, then dynamically allocate each as you need it. And when you do so, they will have exactly what you need inside them. If it's extra work for the sake of a performance hit, I say sh!tcan it.

Or something like that.

ubergeek · #3 04-Jun-2005, 16:19

I would say use regular variables unless, as Dave said, you don't know how many you will need until runtime. Using dynamic allocation creates so many headaches such as pointer dereferencing, deallocation problems, access violations, scope problems, sharing problems, etc, so why bother if it's unnecessary? Also, using a pointer won't save any space because the data still has to exist somewhere, so you are actually creating overhead by requiring 32 (or however many) bits for a pointer.

dsmith · #4 05-Jun-2005, 07:32

Hi edpoole.

I usually use dynamic allocation, but only if it makes sense. In your class, you have date and time variables. There should only be one of these for each instance of A. Therefore, there is no need to make these pointers, just use normal variables.

However, you may have several instances of your class A. This is where I would use pointers and dynamic memory, not in the class itself.

Cheers,
d

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