Delete_if does not work on associations

Rails
1

I tried to user delete_if on an association:

class Group < ActiveRecord::Base
has_many :memberships, :dependent => :destroy
has_many :users, :through => :memberships

…
end

This is the controller method, trying to use delete_if. Although some
elements are removed (s2 < s1), the save method does not update the
association.

def intersect_or_remove_group
other_group = Group.find(params[:group_id])
s1 = @group.users.size
case params[:submit]
when “Intersect”
@group.users.delete_if { |u| !other_group.users.include?(u) }
when “Remove”
@group.users.delete_if { |u| other_group.users.include?(u) }
end
s2 = @group.users.size
if s2 < s1
@group.save
end
redirect_to @group
end

If I rewrite it like this, it works just fine:

def intersect_or_remove_group
other_group = Group.find(params[:group_id])
s1 = @group.users.size
to_be_deleted = Array.new
case params[:submit]
when “Intersect”
@group.users.each { |u| to_be_deleted << u if !
other_group.users.include?(u) }
when “Remove”
@group.users.each { |u| to_be_deleted << u if
other_group.users.include?(u) }
end
to_be_deleted.each { |u| @group.users.delete(u) }
s2 = @group.users.size
if s2 < s1
@group.save
end
redirect_to @group
end

Is this a bug or a feature?

Thanks for any help in advance

Regards

Alexander

2

On Feb 4, 11:33 pm, “[email protected]”
[email protected] wrote:

elements are removed (s2 < s1), the save method does not update the
association.

Looks like delete_if just acts on the target array, not the
association itself (as a slight typing saver you can pass an array to
delete.

Fred

3

Thanks for the hint.

Probably this is a bug, because the association is not updated
correctly. Unfortunately I am not advanced enough in rails to be able
to provide a patch for it.

Alexander alias MrLongleg