Re: [boost] what is the interest of In Place factory

Subject: Re: [boost] what is the interest of In Place factory
From: rodrigue pons (pons.rodrigue_at_[hidden])
Date: 2009-10-29 11:10:03

Haaa okay i see.
Thank you :)

2009/10/29 Stefan Strasser <strasser_at_[hidden]>:
> Am Thursday 29 October 2009 15:35:52 schrieb rodrigue pons:
>> Hello,
>>
>> I was looking about the boost In Place Factory to resolve a problem i
>> got, and there is something i don't understand: what is the advantage
>> of this lib?
>>
>>
>> For example:
>>
>> I get a class A, wich constructor is:
>> A( int, const string& );
>>
>> And an another class, C, that contains an A*. C provides a method to
>> construct this A*:
>> void C::BuildA( int i, const string & str );
>>
>> wich will be called this way:
>> instance_of_C.BuildA( 1, "test" );
>>
>>
>> If now i use the boost In Place Factory, the member function C::BuildA
>> will become:
>>
>> template<class InPlaceFactoryT>
>> void C::BuildA( InPlaceFactoryT const& factory )
>>
>> wich will be called this way:
>> instance_of_C.BuildA( 1, "test" );
>>
>>
>> We can see here that with or wothout the In Place Factory, the code is
>> exactly the same. So i guess there is something i didn't understand.
>> But what?
>
> the type of A might be unknown to the author of C, i.e. dependent on a
> template parameter. so C cannot know the number and types of parameters to
> the constructor of A.
> see boost::optional<> for a use case.
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