Hi,
I have two objects, lets call them Collection and Foobar (see below).
I want to be able to specify the order of foobars in a collection
using e.g.
@collection.foobar_order = [4, 2, 1, 0, 3]
@collection.save
In irb (script/console), stuff like “a = [:a,:b, :c] ; a = [1 2
0].collect {|x| a[x]}” works fine.
Also in irb, “self.foobar_order.collect { |x| self.foobars[x] }”
correctly returns the re-sorted elements.
However, in Collection#do_reorder, “self.foobars = …” does not
update the object’s “foobars”.
Why?
Thank you! 
Code:
def Collection < AR::Base
has_many :foobars, :order => :position
before_validation :do_reorder
private
def do_reorder
self.foobars = self.foobar_order.collect { |x| self.foobars[x] }
self.foobars.each_with_index do |f,i|
f.position = i # save position in DB for later fetching in
correct order
end
end
end
def Foobar < AR::Base
belongs_to :collection
end
Additional info (not strictly needed for my question):
I have looked at acts_as_list’s features, but I do not need to move
objects up and down, and acts_as_list also has the (big) downside of
acting directly on the DB, and not updating the object instances.
All objects get loaded once and all sorting is done use a
Scriptaculous Sortable instance using pure JS, no AJAX (= no server
load). Upon form submit, Sortable saves the current sorting order as
an array in a hidden field called “foobar_order”, which is then used
by the above code.
Possibly related question:
I have tried to implement Array#reorder and Array#reorder! (in-place)
using the above code like
def Array
e.g. " a=[:a,:b,:c] ; o=[1 2 0] ; a.reorder(o) #=> [:b, :c, :a]
def reorder(o)
o.collect {|x| self[x] }
end
def reorder!(o)
self = self.reorder(o)
end
end
reorder works, but reorder! does not work since you cannot assign
something to “self”.
How would you implement in-place reordering of Arrays? Perhaps even
without having to create copies (since it might be an Array of AR
objects)?
Thank you!
Jens