Rails - Jul 2011 - what is the difference between using group_by in a scope as opposed the controller?

In my controller I have this and it works.

@grouped_by_assignable = collection.order("updated_at desc").group_by
{ |assignment| assignment.assignable }

trying to refactor it into a scope on the model as such

scope :grouped_by_assignable, order("updated_at desc").group_by { |
assignment| assignment.assignable }

yields

ArgumentError: Unknown key: #<Project:0x00000102dd5d80>

Any advice?

Thanks,
 - FJM

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On Thu, Jul 14, 2011 at 9:40 AM,
frankjmattia-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org <
frankjmattia-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> In my controller I have this and it works.
>
> @grouped_by_assignable = collection.order("updated_at
desc").group_by
> { |assignment| assignment.assignable }
>
> trying to refactor it into a scope on the model as such
>
> scope :grouped_by_assignable, order("updated_at desc").group_by {
|
> assignment| assignment.assignable }
>
> yields
>
> ArgumentError: Unknown key: #<Project:0x00000102dd5d80>
>
>
group_by is an Array method. You can try doing this instead

scope :recently_updated, order("updated_at desc")

def self.grouped_by_assignable
  recently_updated.group_by { |assignment| assignment.assignable }
end

But beware, this method would return an array not an AR relation

> Any advice?
>
> Thanks,
>  - FJM
>
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>

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> frankjmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > In my controller I have this and it works.
>
> > @grouped_by_assignable = collection.order("updated_at
desc").group_by
> > { |assignment| assignment.assignable }
>
> > trying to refactor it into a scope on the model as such
>
> > scope :grouped_by_assignable, order("updated_at
desc").group_by { |
> > assignment| assignment.assignable }
>
> > yields
>
> > ArgumentError: Unknown key: #<Project:0x00000102dd5d80>
>
> group_by is an Array method. You can try doing this instead
>
> scope :recently_updated, order("updated_at desc")
>
> def self.grouped_by_assignable
>   recently_updated.group_by { |assignment| assignment.assignable }
> end
>
> But beware, this method would return an array not an AR relation
Ah, makes perfect sense... what could I do if I still wanted to create
an AR relation? Is this a use case for #group? I tried that as well
but I couldn''t get it to group the way I needed it to... I think that
because assignable is polymorphic I need to group by assignable_id and
assignable_type... How can I accomplish that?

Thanks again,
- FJM

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On Thu, Jul 14, 2011 at 8:47 PM,
frankjmattia-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org <
frankjmattia-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > frankjmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > In my controller I have this and it works.
> >
> > > @grouped_by_assignable = collection.order("updated_at
desc").group_by
> > > { |assignment| assignment.assignable }
> >
> > > trying to refactor it into a scope on the model as such
> >
> > > scope :grouped_by_assignable, order("updated_at
desc").group_by { |
> > > assignment| assignment.assignable }
> >
> > > yields
> >
> > > ArgumentError: Unknown key: #<Project:0x00000102dd5d80>
> >
> > group_by is an Array method. You can try doing this instead
> >
>
had to correct this, group_by is an Enumerable method.

> > scope :recently_updated, order("updated_at desc")
> >
> > def self.grouped_by_assignable
> >   recently_updated.group_by { |assignment| assignment.assignable }
> > end
> >
> > But beware, this method would return an array not an AR relation
>
> Ah, makes perfect sense... what could I do if I still wanted to create
> an AR relation? Is this a use case for #group? I tried that as well
> but I couldn''t get it to group the way I needed it to... I think
that
> because assignable is polymorphic I need to group by assignable_id and
> assignable_type... How can I accomplish that?
>
>
I''m pretty sure that you can''t get an array of hashes out of
an AR query
so I guess this can''t be done on the database side.

> Thanks again,
> - FJM
>
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>
>

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On Jul 14, 1:47 pm,
"frankjmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<frankjmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> > frankjmat...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > In my controller I have this and it works.
>
> > > @grouped_by_assignable = collection.order("updated_at
desc").group_by
> > > { |assignment| assignment.assignable }
>
> > > trying to refactor it into a scope on the model as such
>
> > > scope :grouped_by_assignable, order("updated_at
desc").group_by { |
> > > assignment| assignment.assignable }
>
> > > yields
>
> > > ArgumentError: Unknown key: #<Project:0x00000102dd5d80>
>
> > group_by is an Array method. You can try doing this instead
>
> > scope :recently_updated, order("updated_at desc")
>
> > def self.grouped_by_assignable
> >   recently_updated.group_by { |assignment| assignment.assignable }
> > end
>
> > But beware, this method would return an array not an AR relation
>
> Ah, makes perfect sense... what could I do if I still wanted to create
> an AR relation? Is this a use case for #group? I tried that as well
> but I couldn''t get it to group the way I needed it to... I think
that
> because assignable is polymorphic I need to group by assignable_id and
> assignable_type... How can I accomplish that?
>
I would have thought that ''group by assignable_type,
assignable_id''
would do the trick

Fred

> Thanks again,
> - FJM
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