block9.ruby

class Greeter
  attr_reader :greeting

  def initialize(greeting)
    @greeting = greeting
  end

  def greet(subject)
    "#{greeting}, #{subject}!"
  end
end

greeter = Greeter.new("Hello")
greet = greeter.method(:greet)


p greet.call("world") # => "Hello, world!"
p greet.("world")     # => "Hello, world!"
p greet["world"]      # => "Hello, world!"
p greet === "world"   # => "Hello, world!"