Feature #21190: Proposal for the Deconstruct Method in the MatchData Class

• Status: Closed
• Assignee: -
• Target version: -

[aristotelesbr (Aristóteles Costa)]

Context:

The MatchData class currently lacks the deconstruct method, which is necessary for extracting values from a string using pattern matching in Ruby.

Current Extraction Method

Currently, extraction can be done as follows:

result = /(\d{2})(\d{2})(\d{9})/.match("5586987654321")

puts result[1] # => "55"
puts result[2] # => "86"
puts result[3] # => "987654321"

Proposed Solution:

Implement the deconstruct method in the MatchData class to allow conversion of the MatchData object into an array, enabling deconstruction of its components.

class MatchData
  def deconstruct
    self.to_a
  end
end

result = /(\d{2})(\d{2})(\d{9})/.match("5586987654321")
result in [_ , country_code, area_code, number]

puts country_code  # => "55"
puts area_code     # => "86"
puts number        # => "987654321"

[jeremyevans0 (Jeremy Evans)]

You can implement this more easily using named captures:

/(?<country_code>\d{2})(?<area_code>\d{2})(?<number>\d{9})/ =~ "5586987654321"
country_code # => "55"
area_code    # => "86"
number       # => "987654321"

I think proper use of named captures should handle most cases where you would want to use the proposed MatchData#deconstruct. The remaining cases would be when you are passing MatchData as an argument to or result of a method call.

If we did want to implement this, it's questionable to me whether MatchData#deconstruct should operate like MatchData#to_a or MatchData#captures (your example implies captures would be a more useful behavior for that use case).

[nobu (Nobuyoshi Nakada)]

• Is duplicate of Feature #18821: Expose Pattern Matching interfaces in core classes added

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

[nobu (Nobuyoshi Nakada)]

Match#destruct and Match#destruct_keys have been defined since ruby 3.2.
Match#destruct is an alias of Match#captures like @jeremyevans0 (Jeremy Evans) wrote, so your regexp match does not match 4-element pattern.

result = /(\d{2})(\d{2})(\d{9})/.match("5586987654321")
p result.deconstruct                                    #=> ["55", "86", "987654321"]
p (result in [_, country_code, area_code, number])      #=> false
p (result in [country_code, area_code, number])         #=> true
p [country_code, area_code, number]                     #=> ["55", "86", "987654321"]