Ruby Struct
A Struct in Ruby is a convenient and elegant way to bundle attributes together without having to write a class with explicit accessor methods.
For example, let’s look at a DTO used with a Rails ActionMailer class:
class EmailDto < Struct.new(:full_name, :email, :date); end
So in a Model we can have something along the lines of:
class Account < ActiveRecord::Base
def activate
self.active = true; self.save
dto = EmailDto.new(self.full_name, self.email, Time.now)
Notifier.deliver_activation_notification(dto)
end
end
… with a Notifier that looks like:
class Notifier < ActionMailer::Base
def activation_notification(dto)
@recipients = dto.email
@from = "newsletters@example.com"
@subject = "Your account is now active!"
@body[:content] = dto
end
end
An interesting, more flexible/dynamic alternative to Struct is OpenStruct. OpenStruct allows the creation of data objects which accept arbitrary attributes at any time.
require 'ostruct' flexie = OpenStruct.new(:music => 'rock') flexie.bands = ['zep', 'sabbath'] flexie.music # => "rock" flexie.bands.first # => "zep"
Of course, attributes can always be assigned blocks:
flexie.hello = Proc.new { puts 'hello world'}
flexie.hello.call # => hello world
In many cases, Structs can offer a more meaningful, more concrete alternative to aspects of what Hashes are currently popular for in Ruby.