Feature #20702: Add `Array#fetch_values`

• Status: Open
• Assignee: -
• Target version: -

[toy (Ivan Kuchin)]

Array and Hash have matching methods to fetch:

• One value using [] (Array also allows fetching multiple with range or two arguments)
• One value with default or exception using fetch method
• Multiple values using values_at method

But only Hash has method fetch_values to fetch multiple values with fallback or raising an exception (see #10017).

hash = {a: 1, b: 2, c: 3}
array = [1, 2, 3]

hash[:b] # => 2
hash[:d] # => nil
array[1] # => 2
array[4] # => nil

hash.fetch(:b) # => 2
hash.fetch(:d) # => IndexError
hash.fetch(:d){ 42 } # => 42
array.fetch(1) # => 2
array.fetch(4) # => IndexError
array.fetch(4){ 42 } # => 42

hash.values_at(:b, :c) # => [2, 3]
hash.values_at(:b, :d) # => [2, nil]
array.values_at(1, 2) # => [2, 3]
array.values_at(1, 4) # => [2, nil]

hash.fetch_values(:b, :c) # => [2, 3]
hash.fetch_values(:b, :d) # => IndexError
hash.fetch_values(:b, :d){ 42 } # => [2, 42]
# missing
array.fetch_values(1, 2) # => [2, 3]
array.fetch_values(1, 4) # => IndexError
array.fetch_values(1, 4){ 42 } # => [2, 42]