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c++.stlsoft - Enforce new?

reply Ilya Minkov <minkov cs.tum.edu> writes:
Hello.

I want to forbid for some of my classes to be instantiated on the stack 
- because the constructor stores the this pointer immediately in a 
searchable static container and the objects need to keep alive for most 
of the duration of the program.

Are there any ideomatic means of doing that?

If that's not a oneliner, i would think that this might be a valuable 
addition to stlsoft libraries.

-eye
Mar 12 2005
parent "Matthew" <admin stlsoft.dot.dot.dot.dot.org> writes:
Hide the ctor and use a Create method (with the same signature as the 
ctor). I use this fairly regularly.

Unfortunately, it's almost impossible to get a workable generic version 
with the current language, due to the hassles with 
const/pointer/reference/value differences with argument forwarding (as 
described in Chapter 23 of your copy of IC++).

The upside is that it is a nice point at which to introduce shims into 
the construction process, which can simplify client code a great deal. 
Here's a snippet from a recent project (with names changed to protect 
client's IP):


    class BaseClass;

    . . .

    class Auditor;
    class Handler;

    . . .

    typedef ::stlsoft::shared_ptr<BaseClass>    BaseClass_ptr;

    . . .

    class SomeClass
        : public BaseClass
    {
    /// \name Types
    ///  {
    public:
        typedef BaseClass   parent_class_type;
        typedef SomeClass   class_type;
    ///  }

    /// \name Construction
    ///  {
    private:
        /// Default constructor
        SomeClass(  Handler     *handler
                ,   char const  *processIdentity
                ,   char const  *channelIdentity
                ,   char const  *auditPoint
                ,   Auditor     &auditor);
    public:
        /// Destructor
        ~SomeClass();

        static BaseClass_ptr    CreateInstance( Handler     *handler
                                            ,   char const 
*processIdentity
                                            ,   char const 
*channelIdentity
                                            ,   char const  *auditPoint
                                            ,   Auditor     &auditor);

        template <typename S1, typename S2, typename S3>
        static BaseClass_ptr    CreateInstance( Handler     *handler
                                            ,   S1 const 
&processIdentity
                                            ,   S2 const 
&channelIdentity
                                            ,   S3 const    &auditPoint
                                            ,   Auditor     &auditor)
        {
            return class_type::CreateInstance(  handler
                                            , 
::stlsoft::c_str_ptr(processIdentity)
                                            , 
::stlsoft::c_str_ptr(channelIdentity)
                                            , 
::stlsoft::c_str_ptr(auditPoint)
                                            ,   auditor);
        }
    ///  }

    . . .

    };


Thus, one can call CreateInstance() with any types for which string 
access shims are defined and available.

In this case, the instance is passed into a shared_ptr, but this 'idiom' 
(if it qualifies as an idiom) works just as well returning pointers, 
should that be appropriate.




"Ilya Minkov" <minkov cs.tum.edu> wrote in message 
news:d0v9cl$1i3$1 digitaldaemon.com...
 Hello.

 I want to forbid for some of my classes to be instantiated on the 
 stack - because the constructor stores the this pointer immediately in 
 a searchable static container and the objects need to keep alive for 
 most of the duration of the program.

 Are there any ideomatic means of doing that?

 If that's not a oneliner, i would think that this might be a valuable 
 addition to stlsoft libraries.

 -eye 

Mar 12 2005