typed¶ ↑

A Ruby library for Typed variables

No more “NoMethodError: undefined method”! We need some typed variables to avoid silly and stealth mistakes.

# Ruby
irb> name = "foo"
irb> name = 10

# Scala
scala> var name = "foo"
scala> name = 10
<console>:8: error: type mismatch;

# Ruby + typed.gem
irb> vars = Typed::Hash.new
irb> vars[:name] = "foo"
irb> vars[:name] = 10
TypeError: name(String) got Fixnum: 10

>> vars = Typed::Hash.new
=> {}

# Class/Module means not values but type definitions
>> vars[:num] = Numeric
>> vars[:num] = 10
=> 10
>> vars[:num] = "a"
TypeError: num(Numeric) got String: "a"

# Types are automatically guessed
>> vars[:foo] = 10
=> 10
>> vars[:foo] = "a"
TypeError: foo(Fixnum) got String: "a"

# Referrence without assigned raises error
>> vars[:xxx]
Typed::NotDefined: 'xxx' is not initialized

# Hash/Array can be used for complex schema.
>> vars[:services] = {Integer => [{Symbol => String}]}
>> vars[:services] = {
     21 => [{:tcp => "ftp"}, {:udp => "fsp"}],
     25 => [{:tcp => "smtp"}],
   }
=> {25=>[{:tcp=>"smtp"}], 21=>[{:tcp=>"ftp"}, {:udp=>"fsp"}]}
>> vars[:services] = {22 => {:tcp => "ssh"}}
TypeError: services({Integer=>[{Symbol=>String}]}) got {Fixnum=>{Symbol=>String}}: {22=>{:tcp=>"ssh"}}

# changes object tells whether a key is changed or not
>> vars = Typed::Hash.new
>> vars.changes.keys
=> [] 
>> vars[:a] = 1
>> vars.changes.keys
=> ["a"] 
>> vars.changes.reset
>> vars.changes.keys
=> []

# events allows user to use callback about :read,:write
>> vars = Typed::Hash.new
>> vars[:a] = 1
>> vars.events.on(:read){|k,v| puts "reading #{k}"}
>> vars[:a]
reading a
=> 1

Love ‘val’, ‘var’ of Scala!!

# [NOTE] val and var must be written in source files.
% cat user.rb
class User
  include Typed::Scala
  val nick  = String
  var pass  = String
end
% bundle exec irb -r typed -r user
>> u = User.new
>> u.nick
Typed::NotDefined: 'nick' is not initialized
>> u.nick = "maiha"
>> u.nick = "no name"
=> Typed::FixedValue: reassignment to nick

• activesupport gem

• must gem

• Typed::Hash can’t assign Class/Module cause they are treated as type definitions

• must gem adds Object#must method

• All keys are forced to String [since: verson 0.2.0]

sudo gem install typed

• github.com/maiha/typed

(The MIT License)

Copyright © 2012 maiha@wota.jp