Hi Laurent,
> (class +Content +Entity)
> (rel data (+Number))
> (rel containers (+List +Joint) contents (+Container))
>
> (class +Container +Entity)
> (rel data (+Number))
> (rel contents (+List +Joint) containers (+Content))
>
> (pool "/tmp/test.db")
>
> (setq objContainer
> (obj
> ((+Container))
> data 52 ) )
> (commit)
>
> (setq objContent
> (obj
> ((+Content))
> data 25 ) )
> (commit)
This is good!
> (put!>
> objContent
> 'containers
> (append (; 'objContent containers) objContainer) )
Note that (; 'objContent containers) is not correct, because the quoted
symbol 'objContent' doesn't evaluate to an entity.
Better would be (; objContent containers). But this wasn't a problem
here, because both expressions still give NIL.
> (show objContent)
> (show objContainer)
OK
> (zap objContainer)
This is the problem! 'zap' should generally not be called in application
code, because it does a hard-core removal of the object, without taking
care of relations.
Use (lose!> objContainer) to clean up all relations as needed, and mark
the object for final deletion. This will happen at the next call of
'dbgc'
(load "@lib/too.l")
(dbgc)
'dbgc' is usually called by a process started from a nightly cron job,
and internally calls 'zap' if the object is not referenced from other
objects.
: (show objContent)
{3} (+Content) # The joint is gone
data 25
: (show objContainer)
T # Object is marked for deletion
contents ({3})
data 52
-> {2}
(Note that the back-link 'contents ({3})' still exists in the "lost"
object. So you still can undo the 'lose>' here with
(keep!> objContainer)
and the full joint would be re-established)
: (dbgc) # Call garbage collector
-> 2
: (show objContainer)
!? (val "X")
{2} -- Bad ID # Object is gone
{2} ?
> Please consider that I'm very new to picolisp (and to lisp more
> generally) so I may make basic mistakes.
No problem! :)
Cheers,
- Alex
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