Encode

About

Encode makes it easy use get meaningful descriptions from encoded values.

task.status = 'P'
task.status.decode # => 'Pending'

It also simplifies using constants to define encoded values and descriptions.

task.status = Task::Status::New
task.status # => 'N'
task.status.decode # => 'New'

Observations

1. Magic numbers and characters make code more difficult to maintain because they don't have instrinsic meaning.
2. Magic strings, while meaningful, make code more difficult to maintain because minor variations can cause subtle problems.
3. Literal values scattered throughout a codebase increase refactoring time and effort.
4. Mapping between encoded values and descriptions shouldn't require a lot of effort.

Using Encoder

Setup

class Task < ActiveRecord::Base
  include Encoder

  code :status do
    Status::New      = "N"
    Status::Pending  = "P"
    Status::Finished = "F"
    Status::OverDue  = "O"
  end

  code :priority do
    Priority::High =  1
    Priority::Low =   5
  end

end

Usage Examples

t = Task.new # => #<Task id: nil, status: nil, priority: nil>

# Using a constant to assign the value
t.status = Task::Status::New # => "N"
t.status # => "N"
t.status.decode # => "New"

# Using a decoded value to assign the value
t.priority = 1 # => 1
t.priority # => 1
t.priority.decode # => "High"

# Obtaining a list of the constant names defined for each attribute
Task::Status.constants # => ["Pending", "New", "OverDue", "Finished"]
Task::Priority.constants # => ["Low", "High"]
Task::Priority.values # => [5, 1]
Task::Priority.mapping # => { "Low" => 5, "High" => 1 }

To Do

• Auto-mixin on init
• Choose a better name
• Use shoulda or rspec
• Obtain list of constant values (for use with validations)

Copyright (c) 2010 Jon Morton, released under the MIT license