STL algorithm to delete all the objects in a container?

Question

Is there a STL utility/algorithm to do delete *the_object_iterator; on all the objects? So that I can clear() safely? The STL container is a set and the objects are pointers to C++ classes created with new.

Boost seems to be the best solution. My goal was to avoid copy-construction on noncopyable classes.

Consider using Boost.PointerContainer instead http://www.boost.org/doc/libs/1_47_0/libs/ptr_container/doc/ptr_container.html — K-ballo, Sep 29 '11 at 20:25
See http://stackoverflow.com/questions/991335/how-to-erase-delete-pointers-to-objects-stored-in-a-vector — Dabbler, Sep 29 '11 at 20:27
It's generally a bad idea to hold pointers in a container, because if the container is destroyed accidentally (via an exception for example) you won't get the opportunity to clean up properly. — Mark Ransom, Sep 29 '11 at 20:30
... to hold raw (dumb) pointers. It's OK to hold smart pointers. A common pattern, in fact. — MSalters, Sep 30 '11 at 07:37
@MSalters Boost.PointerContainer is the best solution. Smart pointers are dumb to me. ;-) — unixman83, Oct 01 '11 at 00:06

score 16 · Answer 1 · answered Sep 29 '11 at 20:26

16

Use a smart pointer to hold the class pointers

std::set<std::unique_ptr<MyClass> > mySet;

answered Sep 29 '11 at 20:26

Praetorian

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didn't notice that was in the std:: namespace – unixman83 Sep 29 '11 at 20:33
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@unixman83: `unique_ptr` is new in C++11. If you don't have it in your compiler yet, you can use `boost::shared_ptr`. – Fred Larson Sep 29 '11 at 20:34

score 10 · Accepted Answer · answered Sep 29 '11 at 20:26

10

As far as I know, there is no standard algorithm to delete all objects. However, you can build up one easily:

template< typename T > invoke_delete( T* ptr ){ delete ptr; }

std::for_each( set.begin(), set.end(), &invoke_delete< set_value_type > );

answered Sep 29 '11 at 20:26

K-ballo

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Or `std::for_each(set.begin(), set.end(), [](T* p){delete p;})` (not a template; substitute T yourself). – MSalters Sep 30 '11 at 07:42
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@MSalters: Indeed, but that's C++11 and I happen to know the OP is working with VC++9. – K-ballo Sep 30 '11 at 07:45

score 7 · Answer 3 · answered Sep 29 '11 at 20:45

Boost pointer containers are the way to go.

Not only do they store the dynamically allocated objects. But the objects are accessible as references which makes using the standard algorithms on the the object that much easier.

boost::ptr_set<MyClass>   setData;

setData.insert(new MyClass);

STL algorithm to delete all the objects in a container?

3 Answers3