I think that's what's always tripped me up. Most ActiveRecord commands
still work normally on the array. I've always chained them and thought I
was building a relation, not getting the array. It wasn't until I had a big
set of records and discovered I couldn't use the association in a find_each
that I tripped over this.
Thanks for the help.
On Friday, June 8, 2012 9:02:45 AM UTC-7, Colin Law wrote:
>
> On 8 June 2012 16:44, Max Reznichenko
> >> order.line_items != LineItem.where(:order_id => order.id)
> >
> > Let me rephrase Robert's words.
> > The key difference here is, that LineItem.where(:order_id => order.id)
> > doesn't fire the sql and returns ActiveRecord::Relation object.
> > While the order.line_items runs SQL and returns the Array of records.
> > The purpose of it is that u can change the resulting SQL and do the
> > method chaining.
> >
> > Try next:
> > line_items_by_order_id = LineItem.where(:order_id => order.id) # =>
> > object of ActiveRecord::Relation class
> > ordered_line_items_by_order_id = LineItem.where(:order_id =>
> > order.id).order(:updated_at) # => object of ActiveRecord::Relation
> > class
> > ordered_line_items_by_order_id_with_positive_price =
> > LineItem.where(:order_id =>
> > order.id).order(:updated_at).where("line_items.price > ?", 20) # =>
> > object of ActiveRecord::Relation class
> > # ... and so on
> > # where
> > order.line_items # returns [LineItem, LineItem ...] array
>
> It is noteworthy that one can still do
> order.line_items.where( some condition )
> even though order.line_items appears to be an Array.
>
> Colin
>
On Friday, June 8, 2012 9:02:45 AM UTC-7, Colin Law wrote:
>
> On 8 June 2012 16:44, Max Reznichenko
> >> order.line_items != LineItem.where(:order_id => order.id)
> >
> > Let me rephrase Robert's words.
> > The key difference here is, that LineItem.where(:order_id => order.id)
> > doesn't fire the sql and returns ActiveRecord::Relation object.
> > While the order.line_items runs SQL and returns the Array of records.
> > The purpose of it is that u can change the resulting SQL and do the
> > method chaining.
> >
> > Try next:
> > line_items_by_order_id = LineItem.where(:order_id => order.id) # =>
> > object of ActiveRecord::Relation class
> > ordered_line_items_by_order_id = LineItem.where(:order_id =>
> > order.id).order(:updated_at) # => object of ActiveRecord::Relation
> > class
> > ordered_line_items_by_order_id_with_positive_price =
> > LineItem.where(:order_id =>
> > order.id).order(:updated_at).where("line_items.price > ?", 20) # =>
> > object of ActiveRecord::Relation class
> > # ... and so on
> > # where
> > order.line_items # returns [LineItem, LineItem ...] array
>
> It is noteworthy that one can still do
> order.line_items.where( some condition )
> even though order.line_items appears to be an Array.
>
> Colin
>
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