[ruby-core:32637] Re: Proposal for Optional Static Typing for Ruby

On Sep 29, 2010, at 9:14 AM, Martin Pilkington wrote:

> When this is compiled I get two warnings. The first about assigning a =
string to a variable typed as an array, the second is that NSArray may =
not respond to 'length'. Now if this was Java those would be compiler =
errors and this code wouldn't run, but as this is Objective-C and =
objects are duck typed then that code does run and it outputs 9. Now I =
can choose to throw away that type information if I wish. The following =
code is exactly the same, except I don't have any of the type checking =
and so get no warnings:

Two quick comments:

1. There are those that would argue that an ignored warning in a =
compiled language is as good as no warning at all.

2. You can already do something similar today with Ruby 1.9:

---
def def_with_types(method_name, args_hash)
 eval("define_singleton_method(method_name) do =
|#{args_hash.keys.join(',')}|
         #{args_hash.map do |key, value|
             "warn 'Warning: #{key} is not of type #{value}' unless =
#{key}.kind_of? #{value}"
           end.join("\n")}
         yield(#{args_hash.keys.join(',')})
       end")
end

def_with_types :say, message: String, count: Fixnum do |message, count|
 count.times { puts message }
end

say("Odelay", 5)
say(5, "Odelay")
---

Notice that if you run this code, you'll get a warning but that won't =
prevent the later error (calling #times on a string).

Cheers,

Josh=