DZone Snippets: tagging code

quote-delineated tag sets

elliottcable (elliott cable) — Thu, 13 Mar 2008 21:16:57 GMT

snippet to surround a tag with “smart quotes” if it contains any odd characters. i.e. to display tags entered in a flickr-like style (space separated except inside quotes)



tag.gsub(/^/,'“').gsub(/$/,'”') if tag[0].match(/[^A-Za-z0-9\-_.]/)

Tag Cloud in Ruby

jnunemaker () — Thu, 06 Jul 2006 17:01:58 GMT

The options.delete with the default looks mildly interesting. Just wanted to remember that.



def font_size_for_tag_cloud( total, lowest, highest, options={} )

 return nil if total.nil? or highest.nil? or lowest.nil?

 #

 # options

 maxf = options.delete( :max_font_size ) || 14

 minf = options.delete( :min_font_size ) || 11

 maxc = options.delete( :max_color ) || [ 0, 0, 0 ]

 minc = options.delete( :min_color ) || [ 156, 156, 156 ]

 hide_sizes = options.delete( :hide_sizes )

 hide_colours = options.delete( :hide_colours )

 #

 # function to work out rgb values

 def rgb_color( a, b, i, x)

  return nil if i <= 1 or x <= 1

  if a > b

   a-(Math.log(i)*(a-b)/Math.log(x)).floor

  else

   (Math.log(i)*(b-a)/Math.log(x)+a).floor

  end

 end

 #

 # work out colours

 c = []

 (0..2).each { |i| c << rgb_color( minc[i], maxc[i], total, highest ) || nil }

 colors = c.compact.empty? ? minc.join(',') : c.join(',')

 #

 # work out the font size

 spread = highest.to_f - lowest.to_f

 spread = 1.to_f if spread <= 0

 fontspread = maxf.to_f - minf.to_f

 fontstep = spread / fontspread

 size = ( minf + ( total.to_f / fontstep ) ).to_i

 size = maxf if size > maxf

 #

 # display the results

 size_txt = "font-size:#{ size.to_s }px;" unless hide_sizes

 color_txt = "color:rgb(#{ colors });" unless hide_colours

 return [ size_txt, color_txt ].join

end

My ColdFusion Tagging Engine/Library

Mozier (Kenny Xiao) — Wed, 15 Mar 2006 07:59:32 GMT

//via:http://www.whatspop.com/blog/2005/12/my-coldfusion-tagging-enginelibrary.cfm













/* Perform a database upload here */

#htmleditformat(left(listgetat(tags_list,tag," "),length))#





Sorry, you need to provide at least one tag

Find items with similar (or as many as possible) relationships - for a 'related posts' box etc

peter (Peter Cooperx) — Mon, 04 Apr 2005 02:00:47 GMT

If we have the id for a post in postid and a limit of num and we want to find posts which share as many tags as possible with postid's post, the following SQL will get you there.

SELECT p.*, COUNT(pt2.post_id) AS count FROM posts p, posts_tags pt, tags t, posts_tags pt2 WHERE pt.post_id=#{postid} AND t.id = pt.tag_id AND pt2.post_id != pt.post_id AND pt2.tag_id=pt.tag_id AND p.id = pt2.post_id GROUP BY pt2.post_id ORDER BY count DESC LIMIT #{num};")

Find all many-to-many relationships which are tied to an arbitrary number of other many-to-many relationships

peter (Peter Cooperx) — Mon, 04 Apr 2005 01:30:28 GMT

Yet more code from Snippets itself. When you narrow down posts by tags, I only want you to see tags which are shared by other posts which also have the same current tags. This is more difficult than it sounds, and requires use of a subselect:

SELECT *, COUNT(pt.post_id) AS count FROM posts_tags pt, tags t WHERE pt.post_id IN (SELECT pt.post_id FROM posts_tags pt, tags t WHERE pt.tag_id = t.id AND (t.name IN ('rails', 'ruby')) GROUP BY pt.post_id HAVING COUNT(pt.post_id)=2) AND t.id = pt.tag_id GROUP BY pt.tag_id ORDER BY count DESC;

The first query (inside the subselect) finds all post IDs for posts which definitely contain any of the current tags. The outer query finds all OTHER tags associated with these posts, therefore we find all (and the quantity of) the tags related to the input tags.

Return items with data intersections over a many-to-many join

peter (Peter Cooperx) — Sun, 03 Apr 2005 22:42:52 GMT

If you have three tables, 'posts', 'tags', and a join table 'posts_tags', and you wish to find all posts which are all associated with a number of different tags, you can use this SQL trick:

SELECT p.* FROM posts_tags pt, posts p, tags t WHERE pt.tag_id = t.id AND (t.name IN ('tag1', 'tag2', 'tag3')) AND p.id=pt.post_id GROUP BY p.id HAVING COUNT(p.id) = 3;

.. where 3 is the number of tags in total. In Ruby/Rails, if you have an array called 'tags' containing the tags, you could use this code:

@posts = Post.find_by_sql ("SELECT p.* FROM posts_tags pt, posts p, tags t WHERE pt.tag_id = t.id AND (t.name = '" + tags.uniq.join ('\' OR t.name=\'') + "') AND p.id=pt.post_id GROUP BY p.id HAVING COUNT(p.id) = " + tags.uniq.length.to_s)

This is how Snippets itself works. You can also add a p.user_id check to the HAVING operator to only find posts with certain tags by a certain user.