Saturday, October 22, 2005

const overloaded arrow operator

I think it is a good idea to have const-overloaded arrow operator in counted pointer idiom though the Coplien's book does not say about it. This is required to "carry forward" the const-ness from the handle object to the body pointer held inside the handle. Counted body idiom is useful when you do not want to add corresponding (mirror) functions in handle class when you add functions in the body class. Handle class can actually be template. (CORBA _var classes?) The arrow operator takes care of "automatic" forwarding.

class String // this is handle
Stringrep *operator -> () const { return b_; }
Stringrep *b_;

class Stringrep // this is body
void func (); // a non-const function.

main() {
const String s (new Stringrep);
s->func (); // invokes a non-const function of stringrep (body) when handle object is const.

In order to prevent this undetected mishap declare vonst-overloaded arrow operators.

class String
const Stringrep *operator -> () const { return b_; }
Stringrep *operator -> () { return b_; }
Stringrep *b_;

Depending upon the const-ness of the handle object, it will invoke the right const-overloaded arrow operator and therefore, const-ness of body pointer comes along with it and therefore, compiler will prevent invocation of non-const member method of the body class using a const handle object. This is important because handle-body are logically the same entity for the client of the abstraction.


Anonymous said...

I enjoyed reading some of your posts. I have a home based business site. You'll find all the information you need about starting your own home based business. There are also great businesses for stay at home moms. Come and check it out if you get time :-)

dat-girl said...

I peep the web for blogs just like this one.
Airtight blog. Your site was off the chain and I will
I will give you access to jump to my 1800contacts web coupon code blog.

stunned said...

Prodigious blog. Loved it so much I went to it
again! Just go online and search for blogs that are
worth the value as yours.
Where you been? You have got to look at my 1800contacts com coupon blog!

lightly-blended said...

Fruitful blog. I favor your site and I shall
return to it! I go to sites like this when I get the
chance, and find blog just like this.
Please examine my 1800contacts com coupon blog as soon as you can.

maryland mortgagee said...

Nice blog. I seen the site and I adored the work,
that I want to visit it more each day! I like
searching for blogs that have the same content like
this one!
Please proceed to my 1800contacts coupon code blog when you find the time.

quick cash advance loan1c1 said...

Super blog. I enjoyed the site and when I have the
time, shall visit the site again. Finding blogs this
good on the internet.
Please consider looking at my blog.

Asset Search said...

Suitable blog, its very good. I liked the site its
from so much I have to visit it again! I surf the web
for blogs like yours in my spare time.
Look who checking out my 1800contacts com coupon blog?

job opportunitya said...

Super blog. I web surf when I have the time for
blogs like this one.Your site was nice and will be
visited again!
Please consider looking at my plastic surgery specialist blog.

job opportunitya said...

Energizing blog. It blew me away and I loved your
site. when I have the time to surf the net, i try
finding blogs as good as your site.
I want you to look for my plastic surgery center blog.