# Parsing a nested set another way **URL:** \ **Category:** Ruby\ **Created:** [April 25, 2009, 10:41pm UTC](https://www.ruby-forum.com/t/parsing-a-nested-set-another-way/166478 "2009-04-25T22:41:43Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![aneeley](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/48db29/32.png) [@aneeley](https://www.ruby-forum.com/u/aneeley)\ **Post date:** [April 25, 2009, 10:41pm UTC](https://www.ruby-forum.com/t/parsing-a-nested-set-another-way/166478/1 "2009-04-25T22:41:43Z")
Hello, new user here. I am trying to render a nested set a certain way. I have code that renders it as a list. But I want to render it another way that I know is possible, but just can’t figure out how to do it. (Look at the attachment for a sketch) Here is my current code: [http://pastie.org/458219](http://pastie.org/458219) . This works, but is not what I want. I think it might be close, though. (I am using Ramaze & DataMapper with nested\_set plugin.) Any advice is appreciated. Thanks in advance. ---
**Author:** ![aneeley](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/48db29/32.png) [@aneeley](https://www.ruby-forum.com/u/aneeley)\ **Post date:** [April 26, 2009, 1:29am UTC](https://www.ruby-forum.com/t/parsing-a-nested-set-another-way/166478/2 "2009-04-26T01:29:43Z")
Adam Neeley wrote: > (I am using Ramaze & DataMapper with nested\_set plugin.) > > Any advice is appreciated. Thanks in advance. > > Attachments: > [http://www.ruby-forum.com/attachment/3622/Photo\_49.jpg](http://www.ruby-forum.com/attachment/3622/Photo_49.jpg) Hi Adam, Your source appears to be eruby (which I don’t know), so I will limit myself to generalities, and pseudocode. You wish to render the data, which is a tree, as a table, you need to know two things before you can start. a) The number of columns in the table (equals the depth of the tree) b) The total number of leaves under each node. (The rowspan or depth of that cell). You will have to compute these by walking the tree. Visit the child nodes before the parent node, telling each child node its depth. It is to increase a global Depth variable if it finds itself deeper than the global depth variable. Thus the global depth variable ends up containing the number of columns the table must have. Each child should return 1 if it has no children The sum of the numbers returned by its children if it has children. so that its parent can accumulate the rowspan of the cell it has to be drawn in. A cell with two children will have to span two rows, one for each child. Its parent will also have to span those two rows. The table generation code then processes the nodes in “pre-order”, generating the content of this node before all of its children. A table starts with “ ”, and sets a global flag to say that “” is required (or “between rows”, before calling the top level nodes one after the other (passing in column No 1). Then each node genereates for itself if the flag is set, it clears it, and generates “”. generates If it has children it calls each of its children in turn (passing in the column number it received, plus 1) otherwise (it has no children), generate the hashed cells to its right… for i in range colNo + 1 to TableWidth generate then it must close the row with and sets the flag to say a “” is needed Then it exits When the last child exits, generates the | | | | where x it the number of leaves calculated above. generates its contents, and closes itself with |   | | | | Set up the css to shade the hashed cells appropriately, and you are done. You can mess with column widths and depths, but I would do as little of this as possible. The default will probably be just fine, and be driven by the size of the content. Regards Ian ---
**Author:** ![aneeley](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/48db29/32.png) [@aneeley](https://www.ruby-forum.com/u/aneeley)\ **Post date:** [April 27, 2009, 1:46am UTC](https://www.ruby-forum.com/t/parsing-a-nested-set-another-way/166478/3 "2009-04-27T01:46:31Z")
Ian, Thank you so much!