send() 方法

send() 用于将消息传递给 object。send() 是 Object 类的实例方法。send() 中的第一个参数是你要发送给对象的消息 - 即方法的名称。它可以是 string 或 symbol，但符号是首选。那些需要传递方法的参数，那些将是 send() 中的剩余参数。

class Hello
  def hello(*args)
    puts 'Hello ' + args.join(' ')
  end
end
h = Hello.new
h.send :hello, 'gentle', 'readers'   #=> "Hello gentle readers"
# h.send(:hello, 'gentle', 'readers') #=> Here :hello is method and rest are the arguments to method.

这是更具描述性的例子

class Account
  attr_accessor :name, :email, :notes, :address

  def assign_values(values)
    values.each_key do |k, v|
      # How send method would look a like
      # self.name = value[k]
      self.send("#{k}=", values[k])
    end
  end
end

user_info = {
  name: 'Matt',
  email: 'test@gms.com',
  address: '132 random st.',
  notes: "annoying customer"
}

account = Account.new
If attributes gets increase then we would messup the code
#--------- Bad way --------------
account.name = user_info[:name]
account.address = user_info[:address]
account.email = user_info[:email]
account.notes = user_info[:notes]

# --------- Meta Programing way --------------
account.assign_values(user_info) # With single line we can assign n number of attributes

puts account.inspect

注意：不再推荐 send() 本身。使用能够调用私有方法的 __send__()，或者（推荐）public_send()