Re: [Boost-users] Assigning 'this' to share_ptr

From: Jeff Foster (jfoster_at_[hidden])
Date: 2008-05-15 14:03:27

See boost::enable_shared_from_this
(http://www.boost.org/doc/libs/1_35_0/libs/smart_ptr/enable_shared_from_this
.html)

> -----Original Message-----
> From: boost-users-bounces_at_[hidden] 
> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of 
> Abdo Haji-Ali
> Sent: 15 May 2008 17:00
> To: boost-users_at_[hidden]
> Subject: [Boost-users] Assigning 'this' to share_ptr
> 
> Hi,
> 
> I was recently introduced to boost's shared_ptr and I really 
> liked the fact that freeing memory is done automatically.
> So I started using it in almost every case, instead of the 
> dangerous C-style pointers.
> However, I'm having a design issue concerning shared_ptr. 
> Here's a snippet that describes my situation:
> 
> <code>
> 
> #include <boost/shared_ptr.hpp>
> 
> class MyClass;
> typedef boost::shared_ptr<MyClass> MyClassPtr;
> 
> class MyClass {
> public:
>    // Fields
>    virtual void CallUtility();    // May be overrided later
> 
>    static MyClassPtr CreateMyClass() {
>        return MyClassPtr(new MyClass());
>    }
> private:
>    MyClass();
> };
> 
> void UtilityFunc(MyClassPtr pClass) {
>    // Do things with pClass
> }
> 
> void MyClass::CallUtility() {
>    // Do stuff
>    // How can I pass 'this' to UtilityFunc?
>    // without freeing it, of course
>    UtilityFunc(MyClassPtr(this)); // How can I pass 'this' to 
> UtilityFunc?
>    // Do stuff
> }
> 
> </code>
> 
> Note that MyClass is always created using 'new' on the heap 
> (never on the stack).
> Also note that a function is not my only case. I also have 
> classes that store a MyClassPtr and there's a function in 
> MyClass that does something like this:
> ClassA MyClass::CreateClassA()
> {
>    ClassA a;
>    a.myClass = this;   // How can I do this
>    return a;
> }
> 
> One way to solve this would be to pass a MyClassPtr parameter 
> to the CallUtility(), and then use it instead of this. So it 
> becomes like this:
> pMyClass->CallUtility(pMyClass);
> 
> Which is ugly, to say the least.
> Do you have another way? Am I missing something trivial here?
> --
> Abdo Haji-Ali
> Programmer
> In|Framez
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