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A tiny rails plugin to assist in simulating enum db types in a db-agnostic fashion
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README.rdoc

EnumSimulator

A simple plugin for abstracting out standard ActiveRecord enumerated attributes

Installation

Let bundler do all the work for you by adding this to your Gemfile:

gem 'enum_simulator'

And then execute:

bundle install

Or install it manually:

sudo gem install enum_simulator

Example

In order to mark an AR attribute as enumerated, make sure the column in question is a string and large enough to accommodate the string representation of your largest possible value. Then, in the model file, just call “enum”, passing it the symbol of the attribute and an array of symbols you'd like to describe as the possible values:

class IceCream < ActiveRecord::Base
  enum :flavor, [:chocolate, :vanilla, :strawberry, :rockyroad]
end

You can also pass a hash to enum, which will automatically validate the attribute's inclusion in the keys of that hash. This is useful for attributes that may need longer human-readable descriptions on display. An example of this:

class PickupTruck < ActiveRecord::Base
  TRUCK_TYPES = {
    :compact_sb => "Compact Short Bed",
    :compact_lb => "Compact Long Bed",
    :compact_ext_sb => "Compact Extended Cab Short Bed",
    :fullsize_sb => "Full-sized Short Bed",
    :fullsize_lb => "Full-sized Long Bed",
    :fullsize_ext_sb => "Full-sized Extended Cab Short Bed"
  }
  enum :truck_type, TRUCK_TYPES
end

And then in a view you can do something like this:

<%= select_tag :truck_type, options_for_select(PickupTruck.enumerated_attributes[:truck_type].map { |k, v| [ v, k ] }) %>

You could also have used the PickupTruck::TRUCK_TYPES constant in this example, but the enumerated_attributes hash is a handy way to access whatever values were passed into the enum definition, especially if you haven't put them in a constant somewhere.

enum_simulator will handle validation of inclusion and conversion of the attribute values from symbols to strings and back internally. Honestly, that's really all it does - it's just such a common pattern that I figured we might as well have a more succinct way of using it. It will infer whether or not to allow assignment of nil to your attribute from the column definition. If your column allows null, then the enumerated_attributes hash for that column will also include nil. This means you do not need an :include_blank in any form tags related to the attribute in question.

Copyright © 2012 Centresource, released under the MIT license

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