Class: Itiel::Transform::SelectColumn

Inherits:
Object
  • Object
show all
Includes:
Nameable, ChainedStep
Defined in:
lib/itiel/transform/select_column.rb

Overview

This transformation only selects specific columns on the data stream

Usage:

@transformer = Itiel::Transform::SelectColumn.new("order_id", "name")

In the example, the output stream would only have the order_id and the name column All other columns will be ignored

Instance Attribute Summary collapse

Attributes included from Nameable

#debug, #step_name

Attributes included from ChainedStep

#next_step

Instance Method Summary collapse

Constructor Details

#initialize(*args) ⇒ SelectColumn

Returns a new instance of SelectColumn.



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# File 'lib/itiel/transform/select_column.rb', line 23

def initialize(*args)
  self.mappings = args
end

Instance Attribute Details

#mappings ⇒ Object

Returns the value of attribute mappings.



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# File 'lib/itiel/transform/select_column.rb', line 17

def mappings
  @mappings
end

Instance Method Details

#input=(stream) ⇒ Object 



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# File 'lib/itiel/transform/select_column.rb', line 19

def input=(stream)
  next_step.input = transform!(stream)
end

#transform!(input_stream) ⇒ Object 



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# File 'lib/itiel/transform/select_column.rb', line 27

def transform!(input_stream)
  selected_output = []
  input_stream.each do |object|
    selected_output << object.select {|key, value| self.mappings.include? key }
  end

  selected_output
end