From: Patrick Bennett <patrick.bennett@...>
Date: 2002-08-27T13:14:44+09:00
Subject: Re: Question about Ruby extension API

In my specific case, I have a Time-derived class that I created through 
the API, and I have a method that needs to adjust the underlying time by 
a specific offset.
I'm trying to do the equivalent of self.+= (fixnum) but it doesn't work.
Why wouldn't I be able to call += or = for my derived-class ?

The class is very simple and adds an instance variable (with 
getter/setter), and a method for 'fixing up' the time (for a specific 
need).  Unfortunately, I haven't found a way for the 'fix up' method to 
modify itself via the inherited Time methods.  
It's a pretty simple requirement, and it's kind of frustrating to run 
into this brick wall after having handled the rest of the API 'fairly 
well'.  It seems odd that a derived-class of Time can't even modify itself.

If I'm reading correctly though, are you saying that I'll have to make 
my method create a new time object, add to it (I'm assuming I >can< call 
Time#+() ?) and return the the new instance ? (forcing the user to call 
x = x.fixup)

Thanks,
Patrick Bennett

Yukihiro Matsumoto wrote:

>Hi,
>
>In message "Question about Ruby extension API"
>    on 02/08/27, "Bennett, Patrick" <Patrick.Bennett@inin.com> writes:
>
>|I've looked all over but can't find the function call for doing a simple assignment (!)
>
>It depends on what you want to assign to.
>
>If it is a local variable, reconsider your design.  You cannot modify
>local variables from within a C function, since a C function is a
>method, and a method cannot modify local variables of outer methods.
>
>If it is an instance variable, use rb_ivar_set().  For a global
>variable, rb_gvar_set() is available.
>
>							matz.
>  
>