I found myself having to reverse logic in some code I wrote recently due to the wants of the client doing a 180. I had been using reject! to remove elements in an array, and realized that I now wanted to use select! - only there is no select!

I started to write:

arr = arr.select{|a| some.method.here }

when it occured to me that was a little clunky. I wanted select in place.

Here’s my version of it:

   1  class Array
   2    def select!(&block)
   3      selected = self.select(&block)
   4      if selected.size > 0
   5        replace(selected) 
   6      else
   7        nil
   8      end
   9    end
  10  end

   1  >> arr = ["Ren", "Easy-E", "Ice Cube", "DJ Yella", "Dr Dre"]
   2  # => ["Ren", "Easy-E", "Ice Cube", "DJ Yella", "Dr Dre"]  
   3  
   4  >> arr.select!{|a| a =~ /^D/ }
   5  # => ["DJ Yella", "Dr Dre"]  
   6  
   7  >> arr.select!{|a| a =~ /^J/ }
   8  # => nil  
   9  
  10  >> arr
  11  # => ["DJ Yella", "Dr Dre"]