C++ Basics: Object Instantiation vs. Dynamic Memory Allocation

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Quick question while learning C++:

Say you have class A, you can instantiate an object of class A like:

A a;

And then you can do stuff with that class (eg, a.method(), etc.)

But you can also do:

A a = new A();

And do stuff with that, and delete it with:

delete a;

My question: What's the difference between the two?

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WittyFool

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Jan 24th, 2006

Re: C++ Basics: Object Instantiation vs. Dynamic Memory Allocation

>What's the difference between the two?
The difference is how you access the object, how long the object lives, and where it's stored.

Narue

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Jan 27th, 2006

Re: C++ Basics: Object Instantiation vs. Dynamic Memory Allocation

Your code wont compile as is. What you need to have is

C++ Syntax (Toggle Plain Text)
void aFunction
{
       A   a;        // create local auto object on the stack
 
       A* ap = new A()  // create object on the heap & have ap refer to it
 
       // do something
 
      delete ap;      // manually delete object that ap refers to
}   // here a & ap are destroyed automatically
void aFunction
{
       A   a;        // create local auto object on the stack

       A* ap = new A()  // create object on the heap & have ap refer to it

       // do something

      delete ap;      // manually delete object that ap refers to
}   // here a & ap are destroyed automatically

kon_t

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