move_lower and move_higher not working returning nil about acts_as_list

[matthewfarrell]

I too had this problem after setting up acts_as_list when there was existing data in the table. It appears that move_lower/move_higher will not move an item if the position column value is null, or if only one item has a position. This makes sense, but is not immediately obvious. To resolve this, I set a default position for all items using a migration:

execute "UPDATE sortable_table SET position = id"

Source: http://nicholshayes.co.uk/blog/?p=344

[swanandp]

@shaileshparamisoft I think upgrading to latest should solve your problem.

[swanandp]

But if not, let me know.

[shaileshkalamkar]

@swanandp Yes, the issue has been resolved.
Thanks for you reply.

[daz]

I'm still getting nil when setting it up, because all my position columns are nil.

[mkolodziej]

I had a Category hierarchy in my app and had the same problem with null position values. I solved it by adding this method to the migration that created the position column:

  update_position_recursively(Category.roots)

  def update_position_recursively(categories)
    categories.each_with_index do |cat, idx|
      cat.update_attribute(:position, idx)
      update_position_recursively(cat.subcategories) unless cat.subcategories.empty?
    end
  end

This is assuming Category.roots would return all roots and that I have has_many :subcategories ... in my Category class

[redbar0n]

I fixed this problem by making a rake task (as DB updates generally shouldn't be done in migrations). See: https://stackoverflow.com/a/15531843/380607