Class: FixedRecord

Inherits:
Object
  • Object
show all
Defined in:
lib/fixed_record.rb

Overview

Provides error-checked simplified access to a YAML data file

Constant Summary collapse

VERSION = 
"0.6.1"

Class Method Summary collapse

Class Method Details

.data(filename, required: [], optional: [], singleton: false) ⇒ Object

Lazy load data from given filename creating accessors for top level attributes



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# File 'lib/fixed_record.rb', line 12

def self.data( filename, required: [], optional: [], singleton: false ) 
  required = required.map( &:to_s )
  optional = optional.map( &:to_s )
  throw ArgumentError, "Required and Optional names overlap" unless (required & optional).empty?

  # Although not necessary, the class_eval makes it easier to see 
  # we are defining variables and methods in the context of the child class which
  # called us
  class_eval do
    # Use @x names for class variables to simplify / restrict access
    @filename = filename
    @valid_keys = Set.new( required )
    @valid_keys.merge( optional )
    @required_keys = Set.new( required )
    @singleton = singleton

    # Load the data and create the methods...
    def self.load!
      return unless @items.nil?
      begin
        y = YAML.load_file( @filename )
      rescue Errno::ENOENT
        raise 
      rescue Psych::SyntaxError => error
        fname = File.basename(@filename)
        msg = error.message
        if msg.include? @filename
          msg.sub!( @filename, fname )
          msg = "#{error.class.name} #{msg}"
        else
          msg = "#{error.class.name} #{fname} #{error.message}"
        end
        raise ArgumentError, msg
      end

      validate_structure( y, @singleton, @filename )

      if @valid_keys.empty? 
        # Grab keys from file
        if @singleton
          @valid_keys = y.keys
        elsif y.is_a?(Array)
          @valid_keys = y.first.keys
          @required_keys = @valid_keys       
        elsif y.is_a?(Hash)
          @valid_keys = y[y.keys.first].keys
          @required_keys = @valid_keys
        end
      end

      if @singleton
        @items = y
      elsif y.is_a?(Array)
        @items = y.map.with_index do |values,i|
          validate_item( @valid_keys, @required_keys, values, i )
          r = new
          r.instance_variable_set( :@values, values )
          r
        end
      elsif y.is_a?(Hash)
        @items = Hash.new
        add_key = !@valid_keys.member?('key')
        y.each do |k,values|
          validate_item( @valid_keys, @required_keys, values, k )
          values['key'] = k if add_key
          r = new
          r.instance_variable_set( :@values, values )
          @items[k] = r   
        end
        define_method( :key ) { @values['key'] }  if add_key
      end
      create_methods( @valid_keys  )
    end

    # filename data was loaded from
    def self.filename
      @filename
    end

    # valid keys (as strings)
    def self.valid_names
      load!
      @valid_keys
    end
  end # class_eval

  if singleton 
    class_eval do # class methods for singleton object
      def self.[](k)
        load!
        k = k.to_s
        raise ArgumentError, "#{k} is not a valid key" unless @valid_keys.member?(k)
        @items[k]
      end
    end # class_eval
  else
    # Add methods for Coillection based objects
    class << self
      include Enumerable
    end
    class_eval do
      def self.all
        load!
        @items
      end

      def self.each( &block )
        all.each(&block)
      end

      def self.size
        all.size
      end

      def self.[]( k )
        if all.is_a?(Hash)
          all[k.to_s]
        else
          nil # Arguably we could index the array, but if we did your code would smell...
        end
      end

      def self.has_item_key?( k )
        if all.is_a?(Hash)
          all.has_key?( k )
        else
          false
        end
      end 
    end #class_eval
  
    # Only way I can find to alias class methods...
    class << self
      alias length size
      alias count size
    end

  end

end

.validate(values, index) ⇒ Object

Override this to perform additional entries. It gets passed the hash containing the values for each record. index is either a record index (0 based) or a key associated with the record



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# File 'lib/fixed_record.rb', line 157

def self.validate( values, index )
end