How to simulate Java-like annotations in ruby?
(We'll I have the answer, generalizing http://bens.me.uk/2009/java-style-annotations-in-ruby)
How to simulate Java-like annotations in ruby?
(We'll I have the answer, generalizing http://bens.me.uk/2009/java-style-annotations-in-ruby)
This is adapted from a piece of code I wrote in an answer to another question a couple of weeks ago, although it is of course hardly original. This is a well-known Ruby idiom, after all, which has been in use for many years, at least since rakes
's desc
method.
module Annotations
def annotations(meth=nil)
return @__annotations__[meth] if meth
@__annotations__
end
private
def method_added(m)
(@__annotations__ ||= {})[m] = @__last_annotation__ if @__last_annotation__
@__last_annotation__ = nil
super
end
def method_missing(meth, *args)
return super unless /\A_/ =~ meth
@__last_annotation__ ||= {}
@__last_annotation__[meth[1..-1].to_sym] = args.size == 1 ? args.first : args
end
end
class Module
private
def annotate!
extend Annotations
end
end
Here's a small example:
class A
annotate!
_hello color: 'red', ancho: 23
_goodbye color: 'green', alto: -123
_foobar color: 'blew'
def m1; end
def m2; end
_foobar color: 'cyan'
def m3; end
end
And of course no Ruby code would be complete without a testsuite:
require 'test/unit'
class TestAnnotations < Test::Unit::TestCase
def test_that_m1_is_annotated_with_hello_and_has_value_red
assert_equal 'red', A.annotations(:m1)[:hello][:color]
end
def test_that_m3_is_annotated_with_foobar_and_has_value_cyan
assert_equal 'cyan', A.annotations[:m3][:foobar][:color]
end
def test_that_m1_is_annotated_with_goodbye
assert A.annotations[:m1][:goodbye]
end
def test_that_all_annotations_are_there
annotations = {
m1: {
hello: { color: 'red', ancho: 23 },
goodbye: { color: 'green', alto: -123 },
foobar: { color: 'blew' }
},
m3: {
foobar: { color: 'cyan' }
}
}
assert_equal annotations, A.annotations
end
end