You could model it as a right-outer join and optional, but I think
that EOF is still going to have a hissy fit when it does not find the
row. Worth a try and a good bug to log with Apple if it does not work.
Chuck
On Jan 13, 2010, at 4:01 PM, Lon Varscsak wrote:
Okay, let me try to give an example (although a contrived example).
Entity: Part (PK: partNumber)
Entity: PartAttributes (PK: partNumber)
It's a to-one relationship from Part to PartAttributes, but the
part_attributes table doesn't have to have a row for a given part.
If this were a to-many relationship this would result in just an
empty NSArray<PartAttributes>. I want partAttributes() to return
null.
In the old days the only way to model this was to have a to-many
relationship with methods that allow the user to access the data in
a to-one way ([[somePart partAttributes] lastObject]). Or you could
but an exception handler in:
- (PartAttributes *)partAttributes {
NS_DURING
[partAttributes self]; //this would catch the exception thrown
NS_HANDLER
[partAttributes release]; //throws away the fault
partAttributes = nil; //sets the ivar to nil
NS_ENDHANDLER
return partAttributes;
}
I was just wondering if this concept of a PK to PK to-one
relationship was possible these days without jumping through hoops.
For this example I probably wouldn't setup the tables this way in
RL, but there are situations where it is valuable and when dealing
with legacy table structures you don't usually have a choice.
-Lon
On Wed, Jan 13, 2010 at 4:49 PM, Chuck Hill <ch...@global-
village.net> wrote:
Modelling it as FK to PK seems like the way to go, unless I am
misunderstanding what you need.
On Jan 13, 2010, at 3:24 PM, Lon Varscsak wrote:
Yes it is the same PK in both tables but there are no rows in the
relationship. This is a pretty common practice and I just hate
modeling a to-many and then provide interfaces as a to-one.
On Wed, Jan 13, 2010 at 4:14 PM, Travis Britt <tbr...@phigment.org>
wrote:
Short answer: no. Is the PK not really a PK? If it is a real PK, how
are there rows without it?
On Jan 13, 2010, at 5:53 PM, Lon Varscsak wrote:
> Is there a way to model an optional to-one relationship from the
primary key to a primary key of another object?
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Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
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