Re: eieio defclass evaluate :initform value

[Joe Riel <joer@san.rr.com>]

On Wed, 04 Jan 2017 12:45:22 -0800
Eric Abrahamsen <eric@ericabrahamsen.net> wrote:

> Joe Riel <joer@san.rr.com> writes:
> 
> > According to the info page for eieio for Emacs 23, one
> > could do
> >
> > (defclass foo-class
> >    ((bar :initform (lambda () my-var)
> >          :type string)))
> >
> > When make-instance was called, the lambda expression
> > for :initform would be evaluated and the expression
> > assigned to my-var would be used for the slot bar.
> >
> > The info page for eieio Emacs 24 does not mention this 
> > functionality and testing shows it no longer exists.
> >
> > Is there nice way, in 24, to create a class with an :initform
> > that, upon instantiation, evaluates to the value of a variable?
> 
> Depending on what exactly you want, you might be able to solve it with
> `oset-default', which lives outside the class definition, and can
> evaluate variables. See if that does what you want?

Thanks, Eric; I wasn't aware of oset-default and could use it, however,
am currently taking a different approach.  The bigger picture is that
I'm using a buffer-local object to store configuration data for a
major mode.  The object is normally updated when the mode is invoked,
but the global defaults should be configurable.  The current approach
is to clone a default object whose values can be assigned via a 
customization.  The documentation for using defcustom with an eieio object
is slim, but I got it working.


-- 
Joe Riel