method

dump

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dump(ary_of_objs, io = "", options = Hash.new) public

This method allows you to serialize an Array of Ruby objects to a String or File of CSV data. This is not as powerful as Marshal or YAML, but perhaps useful for spreadsheet and database interaction.

Out of the box, this method is intended to work with simple data objects or Structs. It will serialize a list of instance variables and/or Struct.members().

If you need need more complicated serialization, you can control the process by adding methods to the class to be serialized.

A class method csv_meta() is responsible for returning the first row of the document (as an Array). This row is considered to be a Hash of the form key_1,value_1,key_2,value_2,… CSV::load() expects to find a class key with a value of the stringified class name and CSV::dump() will create this, if you do not define this method. This method is only called on the first object of the Array.

The next method you can provide is an instance method called csv_headers(). This method is expected to return the second line of the document (again as an Array), which is to be used to give each column a header. By default, CSV::load() will set an instance variable if the field header starts with an @ character or call send() passing the header as the method name and the field value as an argument. This method is only called on the first object of the Array.

Finally, you can provide an instance method called csv_dump(), which will be passed the headers. This should return an Array of fields that can be serialized for this object. This method is called once for every object in the Array.

The io parameter can be used to serialize to a File, and options can be anything CSV::new() accepts.

Show source

# File lib/csv.rb, line 1048
  def self.dump(ary_of_objs, io = "", options = Hash.new)
    obj_template = ary_of_objs.first

    csv = new(io, options)

    # write meta information
    begin
      csv << obj_template.class.csv_meta
    rescue NoMethodError
      csv << [:class, obj_template.class]
    end

    # write headers
    begin
      headers = obj_template.csv_headers
    rescue NoMethodError
      headers = obj_template.instance_variables.sort
      if obj_template.class.ancestors.find { |cls| cls.to_s =~ /\AStruct\b/ }
        headers += obj_template.members.map { |mem| "#{mem}=" }.sort
      end
    end
    csv << headers

    # serialize each object
    ary_of_objs.each do |obj|
      begin
        csv << obj.csv_dump(headers)
      rescue NoMethodError
        csv << headers.map do |var|
          if var[0] == @@
            obj.instance_variable_get(var)
          else
            obj[var[0..-2]]
          end
        end
      end
    end

    if io.is_a? String
      csv.string
    else
      csv.close
    end
  end

dump

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