[elephant-devel] using association slots

[LukasGiessmann]

hello,

thank you for the fast answer everything worked out perfectly.
i was busy with writing exams, so it took me some time to figure
everything out. but as i said before the associations are all performing
well now thanks to you.


take care

lukas



> Hi Lukas,
>
> Were you able to try this example again using the latest checkin?
> Early feedback is better than later!
>
> Thanks,
> Ian
>
> On Jun 17, 2008, at 3:23 PM, LukasGiessmann wrote:
>
>> hello,
>>
>> just in case you're wondering why i'm coming up with questions
>> concerning
>> marc's topic "associations in the elephant system", i'm trying to
>> assist
>> him with this topic, so there might be several questions coming up
>> in the
>> next time - hope you don't mind.
>> to get straight to the point:
>>
>> 1)
>> i tried to work with the last person/job example and the new
>> association
>> slots, so i made the following example:
>>
>> ---
>> (defpclass job()
>>  ((title :initarg :title :accessor title-of :index t)
>>   (company :initarg :company :accessor company-of :index t)))
>>
>> (defpclass person()
>>  ((name :initarg :name :accessor name-of :index t)
>>   (job :initarg :job :accessor job-of :associate t)))
>>
>>
>> (defvar *max-persons* 500)
>> (defvar *max-jobs* 100)
>>
>> (defun make-instances ()
>>  (with-transaction ()
>>    (dotimes (i *max-jobs*)
>>      (let ((current-job (make-instance 'job :title (string (gensym))
>> :company (string (gensym)))))
>> 	(dotimes (j (/ *max-persons* *max-jobs*))
>> 	  (make-instance 'person :name (string (gensym)) :job current-
>> job))))))
>> ---
>>
>> after the call of make-instances there are 100 jobs and for every job
>> there exist 5 persons.
>> but i have still the following problem:
>> how can i get all persons which associate a certain job by using the
>> instance of the job which should be associated by the persons.
>> i thought on something like:
>>
>> ---
>> (defvar *obj* (first (get-instances-by-class 'job)))
>> (get-instance-by-value 'person 'job *obj*)
>> ---
>>
>>
>> 2)
>> what is the better way for using association slots in your opinion,
>> the one of the example above or a special class which contains only
>> associations of jobs and persons?
>>
>> ---
>> (defpclass p-j-assoc()
>>  ((job :initarg :job :accessor job-of :associate t)
>>   (person :initarg :person :accessor person-of :associate t)))
>> ---
>>
>>
>> 3)
>> how do i work with many-to-many association slots, since it is not
>> possible for me to assign a value to the slot.
>>
>> thank you in advance.
>>
>>
>> best regards
>>
>> lukas
>>
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