Class: Hashie::Dash

Inherits:
Hash
  • Object
show all
Defined in:
lib/hashie/dash.rb

Overview

A Dash is a ‘defined’ or ‘discrete’ Hash, that is, a Hash that has a set of defined keys that are accessible (with optional defaults) and only those keys may be set or read.

Dashes are useful when you need to create a very simple lightweight data object that needs even fewer options and resources than something like a DataMapper resource.

It is preferrable to a Struct because of the in-class API for defining properties as well as per-property defaults.

Class Method Summary collapse

Instance Method Summary collapse

Methods included from HashExtensions

#hashie_stringify_keys, #hashie_stringify_keys!, included, #to_mash

Class Method Details

.defaults ⇒ Object

The default values that have been set for this Dash



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# File 'lib/hashie/dash.rb', line 52

def self.defaults
  @defaults
end

.properties ⇒ Object

Get a String array of the currently defined properties on this Dash.



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# File 'lib/hashie/dash.rb', line 41

def self.properties
  @properties.collect{|p| p.to_s}
end

.property(property_name, options = {}) ⇒ Object

Defines a property on the Dash. Options are as follows:

  • :default - Specify a default value for this property, to be returned before a value is set on the property in a new Dash.



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# File 'lib/hashie/dash.rb', line 22

def self.property(property_name, options = {})
  property_name = property_name.to_sym
  
  (@properties ||= []) << property_name
  (@defaults ||= {})[property_name] = options.delete(:default)
  
  class_eval <<-RUBY
    def #{property_name}
      self['#{property_name}']
    end
    
    def #{property_name}=(val)
      self['#{property_name}'] = val
    end
  RUBY
end

.property?(prop) ⇒ Boolean

Check to see if the specified property has already been defined.

Returns:

  • (Boolean) 


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# File 'lib/hashie/dash.rb', line 47

def self.property?(prop)
  properties.include?(prop.to_s)
end

Instance Method Details

#[](property_name) ⇒ Object

Retrieve a value from the Dash (will return the property’s default value if it hasn’t been set).



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# File 'lib/hashie/dash.rb', line 58

def [](property_name)
  super(property_name.to_sym) || self.class.defaults[property_name.to_sym]
end

#[]=(property, value) ⇒ Object

Set a value on the Dash in a Hash-like way. Only works on pre-existing properties.



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# File 'lib/hashie/dash.rb', line 64

def []=(property, value)
  if self.class.property?(property)
    super
  else
    raise NoMethodError, 'You may only set pre-defined properties.'
  end
end