Contents

require "set"

module MARC
  # MARC records contain control fields, each of which has a
  # tag and value. Tags for control fields must be in the
  # 001-009 range or be specially added to the @@control_tags Set

  class ControlField
    # Initially, control tags are the numbers 1 through 9 or the string '000'
    @@control_tags = Set.new(%w[000 001 002 003 004 005 006 007 008 009])

    def self.control_tags
      @@control_tags
    end

    # A tag is a control tag if tag.to_s is a member of the @@control_tags set.
    def self.control_tag?(tag)
      @@control_tags.include? tag.to_s
    end

    # the tag value (007, 008, etc)
    attr_accessor :tag

    # the value of the control field
    attr_accessor :value

    # The constructor which must be passed a tag value and
    # an optional value for the field.

    def initialize(tag, value = "")
      @tag = tag
      @value = value
    end

    # Returns true if there are no error messages associated with the field
    def valid?
      errors.none?
    end

    # Returns an array of validation errors
    def errors
      messages = []

      unless MARC::ControlField.control_tag?(@tag)
        messages << "tag #{@tag.inspect} must be in 001-009 or in the MARC::ControlField.control_tags set"
      end

      messages
    end

    # Two control fields are equal if their tags and values are equal.

    def ==(other)
      if !other.is_a?(ControlField)
        return false
      end
      if @tag != other.tag
        return false
      elsif @value != other.value
        return false
      end
      true
    end

    # turning it into a marc-hash element
    def to_marchash
      [@tag, @value]
    end

    # Turn the control field into a hash for MARC-in-JSON
    def to_hash
      {@tag => @value}
    end

    def to_s
      "#{tag} #{value}"
    end

    def =~(regex)
      to_s =~ regex
    end
  end
end

Version data entries

2 entries across 2 versions & 1 rubygems

Version	Path
marc-1.3.0	lib/marc/controlfield.rb
marc-1.2.0	lib/marc/controlfield.rb