Question

Consider the following code in ruby, assume I called prestart from somewhere:

def tester(process_name, *host_list)
  hosts = []
  hosts = host_list[0]
  hosts[0] = nil
end

def prestart(process_name, *host)
  host_list = ['192.168.1.1', '192.168.1.2'] 
  puts host_list.inspect  # -> ['192.168.1.1', '192.168.1.2']
  tester(process_name, host_list)
  puts host_list.inspect  # -> [nil, '192.168.1.2']
  abort
end

How did it become nil? Is this how ruby works? If yes, how do I make sure it doesn’t effect the caller?

Answer 1

Arrays are objects, and therefore are past by reference. If you want to change it without affecting the original, you need to duplicate it by calling .dup on it. You can do it either in the caller or in the called method.