Class: Remi::SourceToTargetMap::Row

Inherits:
Object
  • Object
show all
Defined in:
lib/remi/source_to_target_map/row.rb

Overview

Public: A row is composed of an array and an index hash. The index hash converts a key into a number representing the position in the array. Functionally, it’s very similar to how a hash works. However, we need to create a lot of Row objects that all have the same index hash. All of those row objects can reference the same index hash object and thus dramatically reduce the amount of memory needed store a lot of rows.

Examples

row = Row.new({ a: 1, b: 2}, ['alpha', 'beta'])
row[:a] #=> 'alpha'
row[:b] #=> 'beta'

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(index, values, source_keys: nil) ⇒ Row

Public: Initializes a row object.

index - A hash containing keys that are usually symbols and values that

represent a position in the values array.

values - An array of values. source_keys - Array of keys that should be treated as data

sources for a row transformation



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# File 'lib/remi/source_to_target_map/row.rb', line 46

def initialize(index, values, source_keys: nil)
  @index = index
  @values = values
  @source_keys = source_keys
end

Class Method Details

.[](arg) ⇒ Object

Public: Converts hash-like objects into rows, array-like objects into rows, or just returns a row if one is provied.

arg - A Row, array-like object, or hash-like object.

Examples:

Row[{ a: 'one', b: 'two' }] #=> #<Row @index={:a=>0, :b=>1} @values=["one", "two"]>

Returns a Row



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# File 'lib/remi/source_to_target_map/row.rb', line 28

def self.[](arg)
  return arg if arg.is_a? Row

  if arg.respond_to? :keys
    Row.new(arg.keys.each_with_index.to_h, arg.values)
  else
    Row.new(0.upto(arg.size).each_with_index.to_h, arg)
  end
end

Instance Method Details

#[](key) ⇒ Object

Public: Returns the value of the row array for the given key



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# File 'lib/remi/source_to_target_map/row.rb', line 53

def [](key)
  @values[@index[key]]
end

#[]=(key, value) ⇒ Object

Public: Sets the value of the row array for the given key



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# File 'lib/remi/source_to_target_map/row.rb', line 58

def []=(key, value)
  @values[@index[key]] = value
end

#each(&block) ⇒ Object

Public: Makes Row enumerable, acts like a hash



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# File 'lib/remi/source_to_target_map/row.rb', line 63

def each &block
  return enumerate_row_variables unless block_given?
  enumerate_row_variables.each { |k,v| block.call(k,v) }
end

#each_source(&block) ⇒ Object

Public: Enumerates over each source value



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# File 'lib/remi/source_to_target_map/row.rb', line 70

def each_source &block
  Enumerator.new do |y|
    source_keys.each { |key| y << [key, self[key]] }
  end
end

#each_target(&block) ⇒ Object

Public: Enumerates over each target value



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# File 'lib/remi/source_to_target_map/row.rb', line 77

def each_target &block
  Enumerator.new do |y|
    target_keys.each { |key| y << [key, self[key]] }
  end
end

#keys ⇒ Object

Public: Returns the keys of the index.



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# File 'lib/remi/source_to_target_map/row.rb', line 89

def keys
  @index.keys
end

#source_keys ⇒ Object

Public: Returns all source keys



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# File 'lib/remi/source_to_target_map/row.rb', line 94

def source_keys
  @source_keys ||= @index.keys
end

#target_keys ⇒ Object

Public: Returns all target keys



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# File 'lib/remi/source_to_target_map/row.rb', line 99

def target_keys
  @target_keys ||= keys - source_keys
end

#to_a ⇒ Object

Public: Returns the values stored in the row.



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# File 'lib/remi/source_to_target_map/row.rb', line 84

def to_a
  @values
end