Module: HasMetadataColumn::ClassMethods

Defined in:
lib/has_metadata_column.rb

Overview

Class methods that are added to your model.

Instance Method Summary collapse

Instance Method Details

#has_metadata_column(column, fields) ⇒ Object

Defines a set of fields whose values exist in the JSON metadata column. Each key in the ‘fields` hash is the name of a metadata field, and the value is a set of options to pass to the `validates` method. If you do not want to perform any validation on a field, simply pass `true` as its key value.

In addition to the normal ‘validates` keys, you can also include a `:type` key to restrict values to certain classes, or a `:default` key to specify a value to return for the getter should none be set (normal default is `nil`). See TYPES for a list of valid values.

Examples:

Three metadata fields, one basic, one validated, and one type-checked.

has_metadata_column(optional: true, required: { presence: true }, number: { type: Fixnum })

Parameters:

  • column (Symbol) —

    (:metadata) The column containing the metadata information.

  • fields (Hash<Symbol, Hash>) —

    A mapping of field names to their validation options (and/or the ‘:type` key).

Raises:

  • (ArgumentError) —

    If invalid arguments are given, or an invalid class for the ‘:type` key.

  • (StandardError) —

    If invalid field names are given (see source).



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# File 'lib/has_metadata_column.rb', line 93

def has_metadata_column(*args)
  fields = args.extract_options!
  column = args.shift

  raise ArgumentError, "has_metadata_column takes a column name and a hash of fields" unless args.empty?
  raise "Can't define Rails-magic timestamped columns as metadata" if Rails.version >= '3.2.0' && (fields.keys & [:created_at, :created_on, :updated_at, :updated_on]).any?
  classes = fields.values.select { |o| o[:type] && !TYPES.include?(o[:type]) }
  raise ArgumentError, "#{classes.to_sentence} cannot be serialized to JSON" if classes.any?

  if !respond_to?(:metadata_column_fields) then
    class_attribute :metadata_column_fields
    self.metadata_column_fields = fields.deep_clone
    class_attribute :metadata_column
    self.metadata_column = column || :metadata
  else
    raise "Cannot redefine existing metadata column #{self.metadata_column}" if column && column != self.metadata_column
    if metadata_column_fields.slice(*fields.keys) != fields
      raise "Cannot redefine existing metadata fields: #{(fields.keys & self.metadata_column_fields.keys).to_sentence}" unless (fields.keys & self.metadata_column_fields.keys).empty?
      self.metadata_column_fields = self.metadata_column_fields.merge(fields)
    end
  end

  fields.each do |name, options|
    if options.kind_of?(Hash) then
      type          = options.delete(:type)
      type_validate = !options.delete(:skip_type_validation)
      options.delete :default

      attribute name

      validate do |obj|
        value = obj.send(name)
        if !HasMetadataColumn.metadata_typecast(value, type).kind_of?(type) &&
            (!options[:allow_nil] || (options[:allow_nil] && !value.nil?)) &&
            (!options[:allow_blank] || (options[:allow_blank] && !value.blank?))
          errors.add(name, :incorrect_type)
        end
      end if type && type_validate
      validates(name, options) unless options.empty? or (options.keys - [:allow_nil, :allow_blank]).empty?
    end
  end

  class << self
    def define_attribute_methods
      super
      metadata_column_fields.keys.each { |field| define_attribute_method field.to_s }
    end

    def define_method_attribute(attr_name)
      return super unless metadata_column_fields.include?(attr_name.to_sym)
      generated_attribute_methods.module_eval <<-RUBY, __FILE__, __LINE__ + 1
        def __temp__#{attr_name}
          options = self.class.metadata_column_fields[:#{attr_name}] || {}
          default = options.include?(:default) ? options[:default] : nil
          _metadata_hash.include?('#{attr_name}') ? HasMetadataColumn.metadata_typecast(_metadata_hash['#{attr_name}'], options[:type]) : default
        end
      RUBY
    end

    def define_method_attribute=(attr_name)
      return super unless metadata_column_fields.include?(attr_name.to_sym)
      generated_attribute_methods.module_eval <<-RUBY, __FILE__, __LINE__ + 1
        def __temp__#{attr_name}=(value)
          attribute_will_change! :#{attr_name}
          old = _metadata_hash['#{attr_name}']
          send (self.class.metadata_column + '='), _metadata_hash.merge('#{attr_name}' => value).to_json
          @_metadata_hash          = nil
          value
        end
      RUBY
    end
  end
end