setup.rb

$LOAD_PATH.unshift(File.expand_path("#{__FILE__}/../../lib")) # Add PROJECT/lib to $LOAD_PATH
require 'stylist'

stylist.rb

BareTest.suite "Stylist" do
  suite "Stylist" do
    suite "Style finding" do
      setup do
        class Foo; end
        module Stylist; class Foo; def initialize(*args); end; end; end
        module Bar; class Foo; end; end
        module Stylist; module Bar; class Foo; def initialize(*args); end; end; end; end
      end
      setup :class, "a class without namespace" do
        @model = Foo.new
        @result = Stylist::Foo
      end
      setup :class, "a class with namespace" do
        @model = Bar::Foo.new
        @result = Stylist::Bar::Foo
      end
      assert "#style_for finds the right Stylist object for :class" do
        equal @result, ::Stylist.send(:style_for, @model)
      end
      assert "#new_stylist_for creates a new Style instance" do
        equal @result.class, ::Stylist.new_stylist_for(@model)
      end
    end
  end
end

stylist_lib.rb

module Stylist

  def new_stylist_for(model, context={})
    style_for(model).new(model, context)
  end

  private

  # @param name<String> The name of the constant to get, e.g. "Merb::Router".
  #
  # @return <Object> The constant corresponding to the name.
  def full_const_get(name)
    list = name.split("::")
    list.shift if list.first.nil? || list.first.strip.empty?
    obj = ::Object
    list.each do |x|
      # This is required because const_get tries to look for constants in the
      # ancestor chain, but we only want constants that are HERE
      obj = obj.const_defined?(x) ? obj.const_get(x) : obj.const_missing(x)
    end
    obj
  end

  def style_for(model)
    begin
      full_const_get(model.class.to_s)
    rescue NameError
      nil
    end
  end

  extend self
end