I don't understand the keywords like attr_reader or property in the following example:
class Voiture attr_reader :name attr_writer :name property :id, Serial property :name, String property :completed_at, DateTime end How do they work? How can I create my own? Are they functions, methods?
class MyClass mymagickstuff :hello end 3 Answers
That are just class methods. In this example has_foo adds a foo method to an instance that puts a string:
module Foo def has_foo(value) class_eval <<-END_OF_RUBY, __FILE__, __LINE__ + 1 def foo puts "#{value}" end END_OF_RUBY end end class Baz extend Foo has_foo 'Hello World' end Baz.new.foo # => Hello World Those are class methods, you can add them to a class, or create your own class that has addition methods. In your own class:
class Voiture def self.my_first_class_method(*arguments) puts arguments end end Or to add to a class:
Voiture.class_eval do define_method :my_second_class_method do |*arguments| puts arguments end end Once such a class method is defined, you can use it like this:
class VoitureChild < Voiture my_first_class_method "print this" my_second_class_method "print this" end There are also ways to do this by adding modules to a class, which is often how rails does such things, such as using a Concern.
You will want to monkey patch the class Module. That's where methods like attr_reader reside.
class Module def magic(args) puts args.inspect end end class A magic :hello, :hi end #=> [:hello, :hi] As The Tin Man mentioned, monkey-patching base-level classes can be dangerous. Consider it like time-traveling into the past and adding something in the past. Just make sure that what you are adding isn't going to overwrite some other event or else you could come back to a Ruby script/timeline that isn't the same one you left.
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