Method.rb

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)

# 也一樣可以透過呼叫 Proc 的方法使用它：
p greet.call("world") # => "Hello, world!"
p greet.("world")     # => "Hello, world!"
p greet["world"]      # => "Hello, world!"
p greet === "world"   # => "Hello, world!"

Could you be more specific?