In Ruby, is there an Array method that combines 'select' and 'map'?

Question

I have a Ruby array containing some string values. I need to:

1. Find all elements that match some predicate
2. Run the matching elements through a transfo

Answer 1

If you have a select that can use the case operator (===), grep is a good alternative:

p [1,2,'not_a_number',3].grep(Integer){|x| -x } #=> [-1, -2, -3]

p ['1','2','not_a_number','3'].grep(/\D/, &:upcase) #=> ["NOT_A_NUMBER"]

If we need more complex logic we can create lambdas:

my_favourite_numbers = [1,4,6]

is_a_favourite_number = -> x { my_favourite_numbers.include? x }

make_awesome = -> x { "***#{x}***" }

my_data = [1,2,3,4]

p my_data.grep(is_a_favourite_number, &make_awesome) #=> ["***1***", "***4***"]