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Ruby: Using named groups in Regex

An alternative of using a multiple assignment for a Regex are named groups. Especially when your Regex becomes more complicates it is easier to understand and to process.


  • In case a string does not match the pattern, .match will return nil.
  • With Ruby 2.4 the result of .match can be transformed to a Hash with named_captures. This allows you to use methods like slice or fetch on the result.

Example with a multiple assignment

PRODUCT_PATTERN = /\A(.+) S\/N:(\w+)\z/ product = "Bosch S/N:WS200LN12" manufacturer, serial_number = product.match(PRODUCT_PATTERN)&.captures # or manufacturer = product[PRODUCT_PATTERN, 1] serial_number = product[PRODUCT_PATTERN, 2]

Example with named groups

PRODUCT_PATTERN = /\A(?<manufacturer>.+) S\/N:(?<serial_number>\w+)\z/ product = "Bosch S/N:WS200LN12" match = product.match(PRODUCT_PATTERN) || {} manufacturer = match[:manufacturer] serial_number = match[:serial_number] # or manufacturer = product[PRODUCT_PATTERN, :manufacturer] serial_number = product[PRODUCT_PATTERN, :serial_number]
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Owner of this card:

Emanuel De
Last edit:
12 days ago
by Emanuel De
captured, groups
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