[boost] Re: yet another utility class

From: Darin Adler (darin_at_[hidden])
Date: 2000-02-06 11:03:55

> auto_restore is no good if you're not restoring the value to its original.
> What's wrong with set_on_exit, I wonder? Just that it doesn't use "auto_" in
> its name? It is perfectly descriptive, I think.

I think that the name "set_on_exit" gives the wrong emphasis.

For similar reasons, I think that "auto_restore" is not such a good name
either, despite what I said in my last message.

I think of these objects as a way to safely set a variable to a value for a
given scope. The fact that the variable is set back to the old value at the
end of the scope is kind of a "detail of implementation", in a way. I don't
think of auto_ptr as a "delete on exit" or auto-destroyer; I think of it as
a way to represent a pointer to an object with controlled lifetime. I don't
focus on the end of lifetime, even though that's where the work of
destroying the object takes place.

That's why I prefer the class that changes the value and changes it back to
the form that just sets a value on exit.

Some others want classes that do arbitrary actions at the end of a block.
But I think those are harder to use. For example, I prefer a class that
represents an open file to one that closes a file when it falls out of
scope, etc.

So I think the name should specify what the class does as a whole (change
the value of a variable for a particular scope, but change it back when the
scope ends) rather than just focusing on what it does at the end of the
scope. I still think that the "auto_" prefix might be a good idea. Maybe
"auto_value_changer" or "auto_value_setter".

    -- Darin