Class: HashMath::Unpivot::Pivot

Inherits:
Object
  • Object
show all
Defined in:
lib/hash_math/unpivot/pivot.rb

Overview

A single pivot definition consists of which columns to coalesce and to where.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(keys:, coalesce_key:, coalesce_key_value:) ⇒ Pivot

keys is an array of keys to include in the un-pivoting. coalesce_key is the new key to use. coalesce_key_value is the new key to use for its corresponding values.



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# File 'lib/hash_math/unpivot/pivot.rb', line 23

def initialize(keys:, coalesce_key:, coalesce_key_value:)
  @keys               = Array(keys)
  @coalesce_key       = coalesce_key
  @coalesce_key_value = coalesce_key_value

  freeze
end

Instance Attribute Details

#coalesce_key ⇒ Object (readonly)

Returns the value of attribute coalesce_key.



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# File 'lib/hash_math/unpivot/pivot.rb', line 16

def coalesce_key
  @coalesce_key
end

#coalesce_key_value ⇒ Object (readonly)

Returns the value of attribute coalesce_key_value.



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# File 'lib/hash_math/unpivot/pivot.rb', line 16

def coalesce_key_value
  @coalesce_key_value
end

#keys ⇒ Object (readonly)

Returns the value of attribute keys.



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# File 'lib/hash_math/unpivot/pivot.rb', line 16

def keys
  @keys
end

Instance Method Details

#expand(base_hash, value_hash) ⇒ Object

The most rudimentary portion of the Unpivoting algorithm, this method works on just one pivot and returns the extrapolated, un-pivoted rows. Takes two hashes as input: the first will serve as the prototype for each returned hash the second will be one to use for value extraction. Returns an array of hashes.



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# File 'lib/hash_math/unpivot/pivot.rb', line 37

def expand(base_hash, value_hash) # :nodoc:
  keys.map do |key|
    base_hash.merge(
      coalesce_key => key,
      coalesce_key_value => value_hash[key]
    )
  end
end