El lunes, 5 de marzo de 2018, 20:55:40 (UTC+1), Jeremy Evans escribió:
>
> On Monday, March 5, 2018 at 9:00:38 AM UTC-8, David wrote:
>>
>> Hi everybody.
>>
>> Look at this code:
>>
>> class Foo < Sequel::Model
>> one_to_many :bars
>> end
>>
>> class Bar < Sequel::Model
>> many_to_one :foo
>> end
>>
>> f = Foo.new
>> b = Bar.new
>> b.foo = f
>> f.bars # => []
>>
>> f2 = Foo.new
>> b2 = Bar.new
>> f.bars # Magic line!
>> b2.foo = f2
>> f2.bars # => [b2]
>>
>>
>> I think first case should return same that second case.
>>
>> We continue with the example:
>>
>> f2.save # Foo object with id 1 and a bar child
>>
>> b3 = Bar.new(foo_id: 1)
>> f3 = b3.foo
>> f3.bars # => [f2]
>>
>>
>> In this case, I think it should return [f2, f3]
>>
>> Do you see these requirements logical? If we have reciprocal and object
>> assignation, I think these are two annoying Sequel effects that go against
>> "least surprise" principle.
>>
>
> No, I don't think this makes sense. First, your example has errors:
>
Arggg!
I am so sorry for the errors. I refer to [b2, b3], as you point.
b2.foo = f2
> # raises Sequel::Error: associated object #<Foo @values={}> does not have
> a primary key
>
> After fixing those issues, let's consider f3.bars. f3 is basically just
> Foo[1], since b3.foo_id is 1. Foo[1].bars doesn't return [f2], it returns
> [b2]. It should never return f2 or f3 because it returns instances of Bar,
> not of Foo. If you are asking if f3.bars should return [b2, b3], no,
> because b3 hasn't been saved to the database yet.
>
I think reciprocal is a good concept, but I don't understand why it works
in some cases and not in others. Loos at the first example. A simple f.bars
before b2.foo = f2 assignment resolves well the reciprocal. But if you do
without first loading bars, reciprocal assignation is avoided. It doesn't
depend of persisted objects.
Second case is, pehaps, subtle, but I think the object representation (with
reciprocals) doesn't depend in Sequel of persisted state, but in this case
it seems so.
Thank you very much, and sorry again for errors :(
--
David
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