Class: ArcFurnace::Filter

Inherits:
Source show all
Defined in:
lib/arc-furnace/filter.rb

Direct Known Subclasses

BlockFilter

Instance Attribute Summary

Attributes inherited from Node

#error_handler, #node_id, #params

Instance Method Summary collapse

Methods inherited from Source

#close, #finalize, #prepare, #row

Constructor Details

#initialize(source:) ⇒ Filter

Returns a new instance of Filter.



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# File 'lib/arc-furnace/filter.rb', line 11

def initialize(source:)
  @source = source
  @value = nil
end

Instance Method Details

#advance ⇒ Object 



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# File 'lib/arc-furnace/filter.rb', line 34

def advance
  loop do
    @value = source.row
    break if value.nil? || filter(value)
  end
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/arc-furnace/filter.rb', line 30

def empty?
  @value.nil? && source.empty?
end

#filter(row) ⇒ Object

Given a row from the source, tell if it should be passed down to the next node downstream from this node.

This method must return a boolean



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# File 'lib/arc-furnace/filter.rb', line 26

def filter(row)
  raise "Unimplemented"
end

#value ⇒ Object 



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# File 'lib/arc-furnace/filter.rb', line 16

def value
  if @value.nil? && !empty?
    advance
  end
  @value
end