Proc and Block

Proc.rb

#---
# Ruby Facts: Proc and Block
#---

#take a block of code (code in between do and end), 
#wrap it up in an object (called a proc), 
# store it in a variable or pass it to a method, 
#and run the code in the block whenever you feel like it
>> toast = Proc.new do
?> puts "cheers!"
>> end
=> #<Proc:0x7fe5a61c@(irb):4>
>> toast.call
cheers!

#blocks can take parameters
>> do_you_like = Proc.new do |good_stuff|
?> puts "I like #{good_stuff}!"
>> end
=> #<Proc:0x7fe54438@(irb):8>
>> do_you_like.call "Ruby"
I like Ruby!

#Methods That Take Procs
def twice_do some_proc
>> some_proc.call
>> some_proc.call
>> end
=> nil
>> wink = Proc.new do
?> puts "wink"
>> end
=> #<Proc:0x7fe50004@(irb):15>
>> twice_do wink
wink
wink

#Passing Blocks (Not Procs) into Methods
#In order to make your method grab the block and turn the block into a proc, 
#put the name of the proc at the end of your method’s parameter list, 
#preceded by an ampersand (&).

>> def profile block_description, &block
>> start_time = Time.new
>> block.call
>> duration = Time.new - start_time
>> puts "#{block_description}: #{duration} seconds"
>> end

>> profile 'count to a million' do
?> number = 0
>> 1000000.times do
?> number = number + 1
>> end
>> end
count to a million: 0.41 seconds

Proc: you can store it or pass it around like you can with any object