This post originated from an RSS feed registered with Scala Buzz by Zemian Deng. Original Post: Sorting a map by it's value Feed Title: thebugslayer Feed URL: http://www.jroller.com/thebugslayer/feed/entries/atom?cat=%2FScala+Programming Feed Description: Notes on Scala and Sweet web framework Latest Scala Buzz Posts Latest Scala Buzz Posts by Zemian Deng Latest Posts From thebugslayer

Question

If we were given a map of id to name as categories data model, how are we going to generate a html drop down input that's sorted by display names?

//example of given data map
val m = Map(
  1111 -> "Music",
  1021 -> "Audio",
  1001 -> "TV & Video",
  5011 -> "Computers",
  9011 -> "Software",
  1311 -> "Phones & Office",
  2011 -> "Cameras & Camcorders",
  1911 -> "Games & Toys",
  6611 -> "Home & Appliances"
)

Answer

Scala map has toList method that will produce a list of tuple(key, value). We can use that and apply the sort with a higher function to sort by the second tuple value.

println("<select name='category'>")
for((k,v) <- m.toList.sort{ (a, b) => a._2 < b._2 }) 
  println("<option value='" + k + "'>" + v + "</option>")
println("</select>")

//This should produce something like this:
<select name='category'>
<option value='1021'>Audio</option>
<option value='2011'>Cameras & Camcorders</option>
<option value='5011'>Computers</option>
<option value='1911'>Games & Toys</option>
<option value='6611'>Home & Appliances</option>
<option value='1111'>Music</option>
<option value='1311'>Phones & Office</option>
<option value='9011'>Software</option>
<option value='1001'>TV & Video</option>
</select>