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.
Top comments (2)
Thanks, Leonid!