There are different ways to define a lambda or proc in ruby. [*]

1. with lambda keyword

   test = lambda do |arg|
     puts arg
   end
   

2. with the lambda literal -> (since Ruby 1.9.1)

   test = ->(arg) do
     puts arg
   end
   

3. with the proc keyword (which defines a lambda that does not test the given number of arguments):

   test = proc do |arg|
     puts arg
   end
   

Growing Rails Applications in Practice

Check out our e-book. Learn to structure large Ruby on Rails codebases with the tools you already know and love.

• Introduce design conventions for controllers and user-facing models
• Create a system for growth
• Build applications to last

Read more Show archive.org snapshot

[*] Technicalities:

• There is only Proc. Both proc and lambda create instances of Proc (but lambda variants do not allow omitting arguments which don't have a default value).
• Proc.new exists, but calling proc is the same as Proc.new Show archive.org snapshot .

And there are different ways to call them:

1. call (we prefer this)

   test.call('hello world')
   

2. Square brackets (could easily be mistaken for a hash)

   test['hello world']
   

3. .() (weird, isn't it?)

   test.('hello world')