Implement forced proxy for to_param

lib/draper/base.rb

@@ -5,6 +5,7 @@ class Base
     attr_accessor :model
 
     DEFAULT_DENIED = Object.new.methods
+    FORCED_PROXY = [:to_param]
     self.denied = DEFAULT_DENIED
 
     def initialize(input)
@@ -45,16 +46,15 @@ def to_model
 
   private  
     def select_methods
-      self.allowed || (model.public_methods - denied)
+      specified = self.allowed || (model.public_methods - denied)
+      (specified - self.public_methods) + FORCED_PROXY
     end
 
     def build_methods
       select_methods.each do |method|
-        unless self.respond_to?(method)
-          (class << self; self; end).class_eval do
-            define_method method do |*args, &block|
-              model.send method, *args, &block
-            end
+        (class << self; self; end).class_eval do
+          define_method method do |*args, &block|
+            model.send method, *args, &block
           end
         end
       end  

spec/base_spec.rb

@@ -17,7 +17,16 @@
     subject.gsub("Sample"){|match| "Super"}.should == "Super String"
   end
 
-  context ".draper" do
+  it "should not override a defined method with a source method" do
+    DecoratorWithApplicationHelper.new(source).length.should == "overridden"
+  end
+
+  it "should always proxy to_param" do
+    source.send :class_eval, "def to_param; 1; end"
+    Draper::Base.new(source).to_param.should == 1
+  end
+
+  context ".decorate" do
     it "should return a collection of wrapped objects when given a collection of source objects" do
       sources = ["one", "two", "three"]
       output = Draper::Base.decorate(sources)

spec/samples/decorator_with_application_helper.rb

@@ -14,4 +14,8 @@ def sample_link
   def sample_truncate
     h.truncate("Once upon a time", :length => 7)
   end
+
+  def length
+    "overridden"
+  end
 end