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dynamic array of interfaces

momond19 asked:

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I have a class MyClass which implements an interface MyInterface:
class MyInterface {
   virtual void myFunction () = 0;
class MyClass : public MyInterface {
    MyClass ();
    virtual ~MyClass ();
    void myFunction ();

Now I want to make a dynamic array of MyClass objects.
My first attempt was:
MyInterface *a;
a = new MyClass[n];
for (int i=0; i<n; i++) {
    a[i].myFunction ();

which failed at runtime for n > 1.

So I come to a possible solution like this:
MyInterface **a;
a = new MyInterface*[n];
for (int i=0; i<n; i++) {
    a[i] = new MyClass ();
    a[i] ->myFunction ();

The problem with this solution is that when I want to reclaim the used resources with:
for (int i=0; i<n; i++) {
    delete a[i];
delete []a;
it really takes a long time, if compared to:
MyClass *a;
a = new MyClass[n];
for (int i=0; i<n; i++) {
delete []a;

I notice that allocating with (A) takes a lot more memory than (B), anyone can explain this?

Tags: C++


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