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Re: owns destination + deny prohibited?
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Re: owns destination + deny prohibited?


  • Subject: Re: owns destination + deny prohibited?
  • From: OCsite via Webobjects-dev <email@hidden>
  • Date: Sun, 27 Feb 2022 15:22:44 +0100

Philippe,

> ... The fact that an EO is deleted when it's removed from the relationship is
> technical consequence of a model. Don't use it because it's practical ...

Um, what other reason is there to use owning relationships? The documentation
says

“If a source object owns its destination object, for example, as when an Agent
object owns its Customer objects, then when something happens so that a
destination object (Customer) is removed from the relationship, it is also
removed from the data source. Ownership implies that an owned object cannot
exist without its owner/”

(in three-odd different places, but always using essentially the same words),
and if there's anything else in there, I can't find it. I might be completely
wrong, but this suggests to me that a deletion of object removed from the
relationship is the very (and also only) purpose of the ”owns” flag?

Thanks and all the best,
OC

> On 27 Feb 2022, at 14:46, Philippe Rabier <email@hidden> wrote:
>
> Hi OC,
>
> When an EO entity A owns an entity  B, consider A and B as a whole. B does
> not exist separately. If you'd use a nosql document database, everything will
> be in the same document. The best and known examples of usage are invoices or
> quotes and their lines.
>
> What you want to do is to prevent deletion depending of other information
> like the invoice status where a hypothetical VALID status would prevent the
> deletion of the invoice. In that case and if you use Wonder, you could raise
> an exception when the method willDelete is called.
>
> However, in your case, I have some doubts that a company owns departments
> because maybe a department is linked to employees or budget or other stuffs …
> a red flag is when you write that all departments must be deleted first
> before the company. The fact that an EO is deleted when it's removed from the
> relationship is technical consequence of a model. Don't use it because it's
> practical in some case ( and in your case, it's not so practical ;-))
>
> Philippe
> ————————————
> Sent from my iPhone
>
>
>> On 27 Feb 2022, at 12:45, OCsite via Webobjects-dev
>> <email@hidden> wrote:
>>
>> Hi there,
>>
>> as I am checking all my relationships to make sure I did not another
>> mistake, I've bumped into something strange.
>>
>> It looks like EOF prohibits a combination of “owns destination” and the
>> “deny” delete rule.
>>
>> Can perhaps anybody explain the rationale behind that?
>>
>> I must be overlooking something of importance, for it seems to me it is
>> quite acceptable approach something like “a company owns all the
>> departments. Whenever one is removed from the relationship, it should be
>> deleted, no point for it existing separately. Still, I want to prevent
>> deletion of a whole company which contains a non-zero number of departments;
>> to prevent user errors, if somebody does want to delete a company, I want
>> him to remove all its departments first”.
>>
>> What am I missing?
>>
>> Thanks,
>> OC
>>
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References: 
 >owns destination + deny prohibited? (From: OCsite via Webobjects-dev <email@hidden>)
 >Re: owns destination + deny prohibited? (From: Philippe Rabier via Webobjects-dev <email@hidden>)

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