I looked really hard in http://www.ruby-doc.org/core-2.1.2/Array.html but I couldn't find a quick functionality to this behaviour:
arr = [1,2,3,4,5,6]
arr.without(3,6) #=> [1,2,4,5]
I know I can write my own function/monkey-patch ruby/add a class method/write it in a few lines.
Is there a way to do this in a ruby way?
you can use subtraction :
arr - [3,6]
EDIT
if you really wanted you could alias this method
class Array
alias except -
end
then you can use:
arr.except [3,6]
Array#- doesn't just subtract. It removes any instance of any item in the supplied parameter. So [1,2,3,3,3] - [2,3] => [1]. This may be something you don't expect.This got added in Rails 5 :)
https://github.com/rails/rails/issues/19082
module Enumerable
def without(*elements)
reject { |element| element.in?(elements) }
end
end
it's just aesthetics, but it makes sense for the brain
There is another way using reject. But it is not cleaner than -
arr.reject{|x| [3,6].include? x}
Just in case anyone else comes across this and is looking for a way to delete elements from an array based on a conditional: you can use delete_if.
For example, I have a list of customers and want to merge any customers that have duplicate emails. After doing a query to get a list of all emails with the total count number for each email, I can then delete all of them that only appear once:
emails = Customer.select('count(email) as num_emails, email').group('email')
emails.delete_if { |email| email.num_emails.to_i == 1 }
The end result is I have a list of all customer emails that appear multiple times in the database.
