what is the difference between using group_by in a scope as opposed the controller?

rubyonrails-talk
1

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

2

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

3

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

4

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.

5

> > 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