Service Locator Pattern - remove the explicit references to external class names. *** I had it in my head to write something that would provide the basics of the service locator pattern. While this will provide all services without error it still leaves t

registry_test.rb

puts __FILE__
require "../service_locator.rb"
require "test/unit"

class TestServiceRegistry < Test::Unit::TestCase
  
  def test_registry
    reg = Service::Registry.new
    assert_not_nil(reg)
    assert_nil(reg[:bob])
    
    reg.register(:foo){"TEST"}
    assert_equal("TEST", reg[:foo])
  end
  
  def test_registry_builder
    b = Service::Builder.new
    b.foo{"TEST1"}
    assert_equal("TEST1", b.registry[:foo])
  end
  
  def test_registry_define
    locator = Service::Registry.define do |b|
      b.bar{BarTest.new(locator)}
      b.foo{FooTest.new(locator)}
    end
    
    bar = locator[:bar]
    assert_instance_of(BarTest, bar)
    
    foo = locator[:foo]
    assert_instance_of(FooTest, foo)
    assert_same(bar, foo.bar)
  end
  
  class FooTest
    attr_reader :bar
    def initialize(locator)
      @bar = locator[:bar]
    end
  end
  class BarTest
    def initialize(locator)
    end
  end
end

service_locator.rb

module Service
  
class Registry
  
  def initialize
    @services = {}
  end
  
  def self.define
    builder = Builder.new
    yield builder
    builder.registry
  end
  
  def register(name, &block)
    name = name.intern if name.respond_to? :intern
    @services[name] = block
  end
  
  def[](key)
    if @services.has_key?(key)
      @services[key] = @services[key].call if @services[key].is_a? Proc
      @services[key]
    end
  end
end

class Builder
  
  attr_reader :registry
  
  def initialize(reg=nil)
    reg ||= Registry.new
    @registry = reg
  end
  
  def method_missing(service_name, &block)
    if block_given?
      @registry.register(service_name, &block)
    end
    nil
  end
end

end