Module: LegacyMigrations::Transformations

Defined in:
lib/legacy_migrations/transformations.rb

Instance Method Summary collapse

Instance Method Details

#from(from_attribute, *args) ⇒ Object

Move data from the fromattribute_ in the ‘from’ table to a column :to in the ‘to’ table

Options

  • :to - (Required) Column in destination table to fill in with value in ‘from’

  • :if - specify a function that takes one parameter (the source table’s RECORD) and returns true or false. The assignment is only made if the function returns a non-false value.

  • &block - if passed a block, the block takes one parameter, which is the value of the attribute in the from parameter, then inserts the result of the block into the destination attribute. parameter and inserts the result of the block in the provided ‘to’ column.

  • :from_record - If you set the “from” column to “from_record”, the variable passed into the block will be the entire from record, instead of just one of its columns



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# File 'lib/legacy_migrations/transformations.rb', line 20

def from(from_attribute, *args)
  options = args.extract_options!

  if options[:if]
    if_method = Proc.new {|record| send(options[:if], record)}
  else
    if_method = Proc.new {|record| true }
  end
  #anyone want to give this a try in another language? ;-)
  custom_method = Proc.new {|record| 
    if if_method.call(record)
      case
      when block_given? && from_attribute == :from_record
        yield(record)
      when block_given?
        yield(record.send(:[], from_attribute.to_s))
      else
        record.send(:[], from_attribute.to_s)
      end
    else
      nil
    end

  }

  @columns.merge!({options[:to] => custom_method})
end

#match_same_name_attributes(*options) ⇒ Object

Shortcut for transferring data between similar tables. For example, if two tables have a column named ‘name’, then using this function will transfer data from source table’s ‘name’ column to the destination table’s ‘name’ column.

Options

  • :only - Array of columns that you want to transfer, and that have the same name on both tables.

  • :except - Array of columns that you DON’T want to transfer, but that have the same name on both tables.



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# File 'lib/legacy_migrations/transformations.rb', line 59

def match_same_name_attributes(*options)

  options = options.extract_options!
  same_name_attributes = @from_table.columns.map(&:name) & @to_table.columns.map(&:name)

  if same_name_attributes
    same_name_attributes = columns_from_options(same_name_attributes, options)
    same_name_attributes.each do |same_name_attribute|
      from same_name_attribute, :to => same_name_attribute
    end
  end
end

#stored(stored_attribute, *args) ⇒ Object 



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# File 'lib/legacy_migrations/transformations.rb', line 72

def stored(stored_attribute, *args)
  options = args.extract_options!

  if options[:if]
    if_method = Proc.new {|record| send(options[:if], record)}
  else
    if_method = Proc.new {|record| true }
  end
  custom_method = Proc.new {|record| 
    if if_method.call(record)
      FutureStorage.instance[@from_table.to_s][record.id][stored_attribute]
    else
      nil
    end
  }
  @columns.merge!({options[:to] => custom_method})
end