Named parameters in Ruby 2

Question

I don\'t understand completely how named parameters in Ruby 2.0 work.

def test(var1, var2, var3)
  puts \"#{var1} #{var2} #{var3}\"
end

test(var3:\"var3-ne         


        

Answer 1

Firstly, the last example you posted is misleading. I totally disagree that the behavior is similar to the one before. The last example passes the argument hash in as the first optional parameter which is a different thing!

If you do not want to have a default value, you can just use nil.

If you want to read a good writeup, see "Ruby 2 Keyword Arguments".

Answer 2

This is present in all the other answers, but I want to extract this essence.

There are four kinds of parameter:

             Required     Optional
Positional | def PR(a)  | def PO(a=1) |
Keyword    | def KR(a:) | def KO(a:1) |

When defining a function, positional arguments are specified before keyword arguments, and required arguments before optional ones.

irb(main):006:0> def argtest(a,b=2,c:,d:4)
irb(main):007:1> p [a,b,c,d]
irb(main):008:1> end
=> :argtest

irb(main):009:0> argtest(1,c: 3)
=> [1, 2, 3, 4]

irb(main):010:0> argtest(1,20,c: 3,d: 40)
=> [1, 20, 3, 40]

edit: the required keyword argument (without a default value) is new as of Ruby 2.1.0, as mentioned by others.