Re: deleting dynamically allocated objects in a container
In article
<4497e00d-a5dd-4c17-af38-8947767cb078@k1g2000prl.googlegroups.com>,
"subramanian100in@yahoo.com, India" <subramanian100in@yahoo.com>
wrote:
Suppose 'Test' is a class. I dynamically allocate few 'Test' objects
and push them into a vector<Test*>. I want to delete the dynamically
allocated 'Test' objects using a Standard Library Algorithm instead of
writing a hand-written 'for loop'.
Following is my attempt: (I am using cout statements in the ctor and
dtor only for understanding purpose).
#include <cstdlib>
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
class Test
{
public:
explicit Test(int arg = 0);
~Test();
private:
int val;
};
inline Test::Test(int arg) : val(arg)
{
cout << "From Test ctor: " << val << endl;
}
inline Test::~Test()
{
cout << "From Test dtor: " << val << endl;
}
inline void delete_pointer(Test* & arg)
{
delete arg;
arg = 0;
}
int main()
{
typedef vector<Test*> Container;
Container c;
c.push_back(new Test(100));
c.push_back(new Test(200));
c.push_back(new Test(300));
for_each(c.begin(), c.end(), delete_pointer);
// just to ensure the element values are zero, print them
cout << c[0] << " " << c[1] << " " << c[2] << endl;
return EXIT_SUCCESS;
}
This porgram compiles fine with g++ and when run, produces the output:
From Test ctor: 100
From Test ctor: 200
From Test ctor: 300
From Test dtor: 100
From Test dtor: 200
From Test dtor: 300
0 0 0
My solution seems to work. But is there a better solution ?
Here is Stroustrup's solution (from TC++PL)
template<class T> T* delete_ptr(T* p) { delete p; return 0; }
void purge(deque<Shape*>& s)
{
transform(s.begin(), s.end() ,s.begin(), &delete_ptr);
}
My question is: in real-world applications, how do the dynamically
allocated objects stored in a container deleted ?
I've used the above in lots of real code, sometimes I turned the
delete_ptr function into a struct with an op(). I've also used smart
pointers quite a bit to delete objects. As in:
vector<shared_ptr<Test> > c;
Boost's shared_ptr class is fine for this sort of thing.