hattr_accessor

A gem/plugin that allows you to define attr_accessors that reference members of a hash.

Installation

gem install shuber-hattr_accessor --source http://gems.github.com
OR
script/plugin install git://github.com/shuber/proxy.git

Usage

The hattr_accessor method requires an option named :attribute which should be a symbol that represents the attribute name of the hash that you want to reference. For example:

class SomeClass
  attr_accessor :my_hash
  hattr_accessor :my_attr, :attribute => :my_hash
end

@some_class = SomeClass.new
@some_class.my_attr = 'test'
@some_class.my_hash # => { :my_attr => 'test' }

You may optionally pass a :type option which will type cast the value when calling the getter method. For example:

class SomeClass
  attr_accessor :my_hash
  hattr_accessor :birth_day, :birth_year, :type => :integer, :attribute => :my_hash
end

@some_class.birth_day = '12'
@some_class.birth_day # => 12

@some_class.birth_year = 2008
@some_class.birth_year # => 2008

This is useful if you're using this gem/plugin with ActiveRecord which will pass values as strings if submitted from a form. For Example:

class SomeController < ApplicationController
  def create
    @some_class = SomeClass.new(params[:some_class])
    @some_class.birth_day # => '12'
    # notice it returns as a string instead of an integer
    # using :type => :integer will fix this
  end
end

The current options (email me for suggestions for others) for :type are:

:string
:integer
:float
:boolean

Example

class CustomField < ActiveRecord::Base
  # has a text or blob attribute named :configuration
  serialize :configuration, Hash
end

class CustomFields::Date < CustomField
  hattr_accessor :offset, :type => :integer, :attribute => :configuration
  hattr_accessor :unit, :reference, :attribute => :configuration

  def default_value
    self.offset.send(self.unit).send(self.reference)
  end
end

@field = CustomFields::Date.new({ :offset => '5', :unit => 'days', :reference => 'from_now' })
@field.configuration # => { :offset => '5', :unit => 'days', :reference => 'from_now' }
@field.default_value # => evaluates 5.days.from_now

Contact

Problems, comments, and suggestions all welcome: shuber@huberry.com