Question

I understand the working of block , proc and lambda experession but what i dont understand that when to use anonymous method in code.

What is the problem which Anonymous solves ?

Answer 1

One of the reasons I use lambdas in this way in Ruby is when I need a closure to capture stuff from the surrounding scope, which for example in smaller scripts I sometimes find more convenient than passing things around as arguments. Other people (ab)use top-level instance variables for that, but I don’t like that much.

Update as requested: Here’s a little example:

shift_timestamp = -> ts do
  t = Time.parse(ts.gsub(',','.')) + options[:time]
  "#{t.strftime("%H:%M:%S")},#{t.usec.to_s[0..2]}"
end

This is for a little tool I wrote for shifting subtitles. It’s a short script and writing it this way allowed me to close over options and access it inside the lambda without having to pass it in. As I said, nothing funky, but for small scripts I sometimes like to do this (where “this” is parsing options, writing 1 or 2 lambdas that use those options, use the lambdas instead of methods later on).