| re: I am new to OOP
Allen Maki wrote:[color=blue]
> /*
> I am new to OOP. I have problem in including an array in a class.
> I would like to know why the following codes can be built
> but can not be compiled. Thanks.
> */
>
> #include <iostream>
> using namespace std;
> class Array
> {
> public:
> int *item;
> int capacity;
> };
>
> int main()
> {
> Array *Jan;
> Jan = new Array;
> Jan->capacity = 5;
>
> for (int i =0; i<5; i++)
> Jan->item[i] = i;
>
> for(i =0; i<5; i++)
> cout << Jan->item[i] << endl;
>
> return 0;
> }[/color]
Style problems aside, there are (at least) three problems with this code:
1. In the second for loop, the variable i is undefined. If you're using an
old C++ compiler this may compile, but with a newer, more
standards-compliant compiler it won.t You need to declare a new loop
variable for the second loop - the 'i' from the fist loop is gone.
for (int i = 0...
2. You never allocated any memory for an array, so assuming you fix the
for-loop scoping problem, the code will likely crash at runtime.
3. You used std::endl without #include-ing <iomanip>.
Here's a revised version to point you in the right direction:
#include <iostream>
#include <iomanip>
using namespace std;
class Array
{
private:
int* m_item;
int m_capacity;
public:
Array(int cap)
: m_capacity(cap),
m_item(new int[cap])
{
}
int& operator[](int index)
{
return m_item[index];
}
int capacity() const
{
return m_capacity;
}
};
int main()
{
Array Jan(5);
for (int i =0; i<5; i++)
Jan[i] = i;
for(int i =0; i<5; i++)
cout << Jan[i] << endl;
return 0;
}
-cd
| 
