`:dataset` option is unreachable in another dataset method of model. You
can write `album.potential_listeners_dataset`, but you can't
`Album.potential_listeners_dataset`. But OK, I understood you, thanks.
On Tuesday, December 19, 2017 at 7:59:04 PM UTC+3, Jeremy Evans wrote:
>
> On Tuesday, December 19, 2017 at 8:01:00 AM UTC-8, Alexander Popov wrote:
>>
>> Custom dataset methods force duplicate code.
>>
>
> Sometimes duplicate code is necessary.
>
>
>> Example of desired code:
>>
>> Sequel::Model.plugin :dataset_associations
>>
>> class Area < Sequel::Model
>> # has PostgreSQL `polygon`
>>
>> many_to_one :album
>>
>> one_to_many :included_locations, class: 'Location' do |ds|
>> ds
>> .join(
>> Sequel[:areas].as(:joined_areas),
>> Sequel.lit('locations.point <@ joined_areas.polygon')
>> )
>> .where(
>> Sequel[:joined_areas][:id] =>
>> defined?(id) ? id : Sequel[:areas][:id]
>> )
>> end
>> end
>>
>> class Album < Sequel::Model
>> # has `selling_areas` with PostgreSQL `polygon`
>>
>> one_to_many :selling_areas, class: Area
>>
>> one_to_many :potential_listeners, class: 'Listener' do |ds|
>> selling_areas.included_locations.listeners
>> end
>>
>
> This is probably going to break things, the block should return a modified
> dataset, not a complete new dataset.
>
> You probably want to join or use a subquery in the block, and you may want
> to use the :dataset option instead of a block.
>
> Associations can't handle every possible case. In more complex cases, you
> will need to write the dataset code manually.
>
> Thanks,
> Jeremy
>
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