An example to understand the yield keyword in ruby.

ruby_yield_example.rb

def greeting
  puts '2'
  yield
end

puts '1'
greeting { puts '3'}

=> 1
=> 2
=> 3

# -------------------------------------------------------- #

def welcome(input)
  puts '2'
  puts "#{input}"
  yield
end

puts '1'
welcome(3) { puts '4' }

=> 1
=> 2
=> 3
=> 4

# -------------------------------------------------------- #

def welcome(input)
  puts '2'
  puts "#{input}"
  yield(input)
end

puts '1'
welcome(3) { |x| puts "#{x} * 2 is #{x*2}" }

=> 1
=> 2
=> 3
=> 3 * 2 is 6

# -------------------------------------------------------- #