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From Steve Downey <steve.dow...@netfolio.com>
Subject Re: [lang] Ideas for Lang
Date Sat, 12 Oct 2002 20:48:58 GMT
On Friday 11 October 2002 07:49 pm, Henri Yandell wrote:
> On Fri, 11 Oct 2002, Steve Downey wrote:
> > > 2) Mutable primitive classes. Pondered this at the hospital today. Do
> > > we want such things? new MutableInteger();   mi.setValue(42); etc. Same
> > > for MutableString.
> >
> > I'm not so sure about Mutable value classes. I'd want to see a use case
> > for them first. IOW, what does it gain over this.value = new Integer(42)?
> > If there's shared mutable state, I think it's usually within the same
> > class. I don't see the utility of a mutable Integer that's shared between
> > unrelated classes. And within the same class, I'd think just using
> > members is more natural.
>
> Yeah, my reaction was to think no. But then I decided that discussion on
> it would be very interesting :)
>
I figured out what they are for.
Let's say you have something observing a String, for display or whatever. If 
the value changes, you want the new value displayed. The entity doing the 
display shouldn't care what the String represents. So if it has a 
MutableString, and registers for notifications of changes of the 
MutableString, it can update whenever the String changes.

They're kind of like Delegates for properties. 

What do you think?


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