Module: ValuesFor::SingletonMethods

Defined in:
lib/values_for.rb

Instance Method Summary collapse

Instance Method Details

#values_for(*args) ⇒ Object

Creates an enumerable attribute on an ActiveRecord model. Usage is as follows:

values_for :state, :has => [ :new, :composed, :served, :eaten ]

Any additional options will be passed directly to the ActiveRecord method :validates_inclusion_of, which is used to validate the assigned values to this attribute. Requires a column of type VARCHAR with the name of the first argument to values_for.

Raises:

  • (ArgumentError) 


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# File 'lib/values_for.rb', line 18

def values_for(*args)
  opts        = args.extract_options!
  attribute   = args.first
  
  attribute_s = attribute.to_s

  additives         = Array.wrap(opts[:add])
  plural_attribute  = attribute_s.pluralize
  
  prefix = opts.has_key?(:prefix) ? opts[:prefix] : attribute_s

  # We don't accept the case where an empty string is a valid value, but we should provide a useful error message
  raise ArgumentError, "Can't use values_for with an empty string" if opts[:has].any?{|v| v.respond_to?(:empty?) && v.empty? }
  
  # Valid values are most likely Symbols anyway, but coerce them to be safe.
  valid_symbols = opts[:has].map{|v| v.to_sym }

  valid_symbols.each do |val_sym|
    val_s = val_sym.to_s
    
    prefixed_val = [ prefix, val_s ].compact.join('_')
    
    # Create +optional+ constants
    const_set(prefixed_val.upcase, val_sym) if additives.include?(:constants)
    
    # Create +optional+ named scopes
    named_scope prefixed_val, :conditions => { attribute => val_s } if additives.include?(:named_scopes)

    # Create +optional+ predicate methods, but don't overwrite existing methods
    if additives.include?(:predicate_methods) && !self.instance_methods.include?(prefixed_val)
      define_method(prefixed_val + '?') do    # def foo?
        read_attribute(attribute) == val_s    #   read_attribute(:foo) == 'foo'  
      end                                     # end
    end
  end
  
  # Accepts assignment both from String and Symbol form of valid values.
  validates_inclusion_of attribute, opts.except(:has, :prefix, :add).
    merge(:in => valid_symbols | valid_symbols.map{|s| s.to_s } )
  
  # Custom reader method presents attribute value in Symbol form.
  define_method(attribute_s) do                             # def foo
    unless self[attribute].nil? || self[attribute].empty?   #   unless self[:foo].nil? || self[:foo].empty?
      self[attribute].to_sym                                #     self[:foo].to_sym unless self[:foo].nil?
    end                                                     #   end
  end                                                       # end
  
  # Custom setter method casting all attribute input to String, allows 
  # assignment from Symbol form.
  define_method(attribute_s + '=') do |other|         # def foo=(other)
    self[attribute] = other.nil? ? nil : other.to_s   #   self[foo] = other unless other.nil?
  end                                                 # end
  
  # Make collection of all valid attribute Symbols available to user
  # from plural name of attribute as class method.
  cattr_reader plural_attribute.to_sym
  class_variable_set(:"@@#{plural_attribute}", opts[:has])    
end