Hi,
I browse through C++ primer. I have a question about the calling of
copy constructor in the example of that book. Below, "item" is an
associate container. In main func, there is a call of add_item. From
debug, I see add_item calls "Sales_item(const Sales_item &i)". My
question is: why add_item calls the copy constructor. To you, it may
be very easy. For a beginner like me, I don't know now. Could you give
me an explanation about that? Thanks in advance.





..........................
class Basket {
....
public:
....
void add_item(const Sales_item &item)
{items.insert(item); }

private:
std::multiset<Sales_item, Comp> items;
};
....
class Sales_item {
friend class Basket;
public:
....
// copy control members to manage the use count and pointers
Sales_item(const Sales_item &i):
p(i.p), use(i.use) { ++*use; }

private:
...
};

fl wrote:
> Hi,
> I browse through C++ primer. I have a question about the calling of
> copy constructor in the example of that book. Below, "item" is an
> associate container. In main func, there is a call of add_item. From
> debug, I see add_item calls "Sales_item(const Sales_item &i)". My
> question is: why add_item calls the copy constructor. To you, it may
> be very easy. For a beginner like me, I don't know now. Could you give
> me an explanation about that? Thanks in advance.
>
>
>
>
>
> .........................
> class Basket {
> ...
> public:
> ...
> void add_item(const Sales_item &item)
> {items.insert(item); }

'std::multiset' makes copies of things that you insert. That's
just how all standard containers work.

>
> private:
> std::multiset<Sales_item, Comp> items;
> };
> ...

V
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