Creating a ruby class with mass assignment


#1

Hi,
How do I create a ruby class that has mass assignment functionality? I
want it to work in a similar way to the way in which ActiveRecord does,
ie.
MyClass.new
=> #MyClass:
MyClass.new(:name => “Cool class”)
=> #<MyClass: @name=“s”>
MyClass.new(:name => “Cool class”, :other_attribute => “some other”)
=> #<MyClass: @name=“s”, @other_attribute=“some other”>

I have found the following code snippit which works for the mass
assignment part but doesn’t work if I initialize the class without any
arguments:

class MyClass
attr_accessor :name
attr_accessor :other_attribute

def initialize(args)
args.keys.each { |name| instance_variable_set “@” + name.to_s,
args[name] }
end
end

MyClass.new
ArgumentError: wrong number of arguments (0 for 1)
from (irb):19:in initialize' from (irb):19:innew’
from (irb):19

What is the best way of achieving mass assignment whilst still allowing
to initialize without parameters?


#2

What is the best way of achieving mass assignment whilst still allowing
to initialize without parameters?

def initialize(args = {})
args.keys.each { … }
end


#3

2009/1/30 Ruby N.y removed_email_address@domain.invalid:

args[name] }
to initialize without parameters?
You can make your life considerably easier by using Struct:

irb(main):001:0> Test = Struct.new :foo, :bar, :baz do
irb(main):002:1* def self.create(h = {})
irb(main):003:2> new(*members.map {|m| h[m.to_sym]})
irb(main):004:2> end
irb(main):005:1> end
=> Test
irb(main):006:0> Test.create(:foo => 1)
=> #
irb(main):007:0> Test.create(:bar => 3, :foo => 123)
=> #

Kind regards

robert