map::erase

[Viral Shah]

I have a map<int, obj>. When I do a map::erase(iter ator), does this call the
destructor of the object? Or does it just remove that entry from the map.

[Victor Bazarov]

Re: map::erase

Viral Shah wrote:[color=blue]
> I have a map<int, obj>. When I do a map::erase(iter ator), does this call the
> destructor of the object? Or does it just remove that entry from the map.[/color]

The entry in the map _contains_ the object. Of course while removing the
entry, it _has_to_ destroy the object.

V

[John Dibling]

Re: map::erase

Viral Shah wrote:[color=blue]
> I have a map<int, obj>. When I do a map::erase(iter ator), does this call the
> destructor of the object? Or does it just remove that entry from the map.[/color]

It calls the destructor. A note: if the map is actually a map of
pointers to obj's and not actually obj's themselves, then what is
destroyed is the pointer to the obj - not the obj itself. In other
words, erase doesn't call 'delete' for you if the map is declared like
this: 'map<int, obj*>'.

Take care,

John Dibling

[verec]

Re: map::erase

On 2005-06-21 21:46:53 +0100, "John Dibling" <jdibling@gmail .com> said:
[color=blue]
> Viral Shah wrote:[color=green]
>> I have a map<int, obj>. When I do a map::erase(iter ator), does this call the
>> destructor of the object? Or does it just remove that entry from the map.[/color]
>
> It calls the destructor. A note: if the map is actually a map of
> pointers to obj's and not actually obj's themselves, then what is
> destroyed is the pointer to the obj - not the obj itself. In other
> words, erase doesn't call 'delete' for you if the map is declared like
> this: 'map<int, obj*>'.[/color]

But it *does* call delete if your map is of the form map<int, smart_ptr<T> >
for some suitable definition of smart_ptr<T>

I know: I'm using this all the time :-)
--
JFB

[Victor Bazarov]

Re: map::erase

verec wrote:[color=blue]
> On 2005-06-21 21:46:53 +0100, "John Dibling" <jdibling@gmail .com>
> said:[color=green]
>> Viral Shah wrote:[color=darkred]
>>> I have a map<int, obj>. When I do a map::erase(iter ator), does this
>>> call the destructor of the object? Or does it just remove that
>>> entry from the map.[/color]
>>
>> It calls the destructor. A note: if the map is actually a map of
>> pointers to obj's and not actually obj's themselves, then what is
>> destroyed is the pointer to the obj - not the obj itself. In other
>> words, erase doesn't call 'delete' for you if the map is declared
>> like this: 'map<int, obj*>'.[/color]
>
> But it *does* call delete if your map is of the form map<int,
> smart_ptr<T> > for some suitable definition of smart_ptr<T>
>
> I know: I'm using this all the time :-)[/color]

But that's not the feature of the map. It's the destruction of the
'smart_ptr<T>' object what does the 'delete'ion.

V

[verec]

Re: map::erase

On 2005-06-22 02:36:42 +0100, "Victor Bazarov" <v.Abazarov@com Acast.net> said:
[color=blue]
> verec wrote:[color=green]
>> On 2005-06-21 21:46:53 +0100, "John Dibling" <jdibling@gmail .com>
>> said:[color=darkred]
>>> Viral Shah wrote:
>>>> I have a map<int, obj>. When I do a map::erase(iter ator), does this
>>>> call the destructor of the object? Or does it just remove that
>>>> entry from the map.
>>>
>>> It calls the destructor. A note: if the map is actually a map of
>>> pointers to obj's and not actually obj's themselves, then what is
>>> destroyed is the pointer to the obj - not the obj itself. In other
>>> words, erase doesn't call 'delete' for you if the map is declared
>>> like this: 'map<int, obj*>'.[/color]
>>
>> But it *does* call delete if your map is of the form map<int,
>> smart_ptr<T> > for some suitable definition of smart_ptr<T>
>>
>> I know: I'm using this all the time :-)[/color]
>
> But that's not the feature of the map. It's the destruction of the
> 'smart_ptr<T>' object what does the 'delete'ion.[/color]

Yep. That's the point of using something that can sort of "delegate"
the destruction to the real thing, yet also pose as, the real thing
when accessed from the map.
--
JFB