Question

In my rails app, i have the following function in one of my controller page.

def tree
@jstree = Sub.find_by_sql("Select sequence, depth, node, imageid, range from.....several joins")
end

I now want to loop through the resultset and perform some actions depending on the value of the prev and next row.

<% @jstree.each do |tree| %>
<%= tree.sequence %>
<% end %>

I would like to know how to get the next and previous row value within the above loop

Many many thanks for all suggestions provided 🙂

Answer 1

It depends on how you actually need to use it (and obviously the first and last records won’t have previous/next elements).

If you do an each_with_index you have the index and can use normal array access:

@jstree.each_with_index do |elem, n|
    prev_elem = @jstree[n-1] unless n == 0
    next_elem = @jstree[n+1] unless n == @jstree.size-1
    # Etc.
    do_stuff_with_next if next_elem # Or
    if next_elem
        do_stuff
        do_other_different_stuff
    end
end