RelinkableHandle

[emmajyu]

Hi, I have problem understanding the Handle, RelinkableHandle classes. Why do we need the RelinkableHandle? Here is function of linkTo in the RelinkableHandle class: template inline void RelinkableHandle::linkTo(const boost::shared_ptr& h, bool registerAsObserver) { this->link_->linkTo(h,registerAsObserver); } It does not do anything different from the base class but calling the baseClass link_->linkTo, I dont see diff from the base class here at all. Why do we still need the RelinkableHandle class? Thanks a lot for your help!

[Luigi Ballabio]

Hi Emma,
    inside RelinkableHandle::linkTo, we don't call the linkTo method
of the base class; instead, we call the linkTo method of the protected
link_ data member, which is not accessible from the outside.  The
Handle base class doesn't have a linkTo method, so you can't relink
it.

The general idea is that you'll set up a number of relinkable handles
which will be linked to the current market conditions and passed to
the instruments that need them.  The main code will create them as
RelinkableHandle instances, so that it can relink them if necessary
(and all instruments will see the change).  Instead, when they are
passed to the instruments, they are converted and saved as Handle
instances; this prevent the instruments from changing them. The
instruments have no reason to do it; if they want to change the curves
or the quotes they're using in order to perform some
calculations---calibrations, minimizations, whatever---they should use
copies of the handles instead, because changing the very handles they
are using would have consequences on all the other instruments that
happen to share those handles. Preventing Handle instances from
relinking helps avoiding this error.

Hope this helps,
    Luigi



On Tue, Jun 4, 2013 at 9:49 PM, emmajyu <[hidden email]> wrote:

> Hi, I have problem understanding the Handle, RelinkableHandle classes. Why
> do we need the RelinkableHandle? Here is function of linkTo in the
> RelinkableHandle class: template inline void RelinkableHandle::linkTo(const
> boost::shared_ptr& h, bool registerAsObserver) {
> this->link_->linkTo(h,registerAsObserver); } It does not do anything
> different from the base class but calling the baseClass link_->linkTo, I
> dont see diff from the base class here at all. Why do we still need the
> RelinkableHandle class? Thanks a lot for your help!
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