How to Access Hash Values Like Methods in Ruby

In Ruby, if you want to access hash values like methods on an object, use ActiveSupport::OrderedOptions. This class inherits from Hash and provides dynamic accessor methods.

Typically, you'd do this with a Hash.

person = { name: "Jason", company: "Basecamp" } person[:company] # 'Basecamp' 

Using OrderedOptions, you can write

require "active_support/ordered_options" person = ActiveSupport::OrderedOptions.new # set the values person.name = "Jason" person.company = "Basecamp" # access the values person.name # => 'Jason' person.company # => 'Basecamp' 

Implementation

Behind the scenes, Rails implements this feature using metaprogramming in Ruby. It uses the method_missing method to handle the method call.

def method_missing(name, *args) name_string = +name.to_s if name_string.chomp!("=") self[name_string] = args.first # set the value else bangs = name_string.chomp!("!") # get the value if bangs self[name_string].presence || raise(KeyError.new(":#{name_string} is blank")) else self[name_string] end end end 

You can read the complete source code here. For more details on metaprogramming in Ruby, read my notes of the Metaprogramming Ruby 2 book.

Real-World Usage

Propshaft is an asset pipeline library for Rails. It uses OrderedOptions to define the config.assets settings, instead of creating a new configuration object. You can read the complete source on Github.

class Railtie < ::Rails::Railtie config.assets = ActiveSupport::OrderedOptions.new config.assets.paths = [] config.assets.excluded_paths = [] config.assets.version = "1" config.assets.prefix = "/assets" end 

Now, this doesn't mean you have to replace all your hashes with instances of OrderedOptions. It's better to use them with configuration-like objects, which often results in more readable code.

Hope that helps. Let me know what you think about this approach.