ask for custom constraints by name

lib/raptor.rb

@@ -43,9 +43,20 @@ def injectables
     def find_method(method_path)
       DelegateFinder.new(@app_module, method_path).find
     end
+
+    def constraint_named(name)
+      raise NoSuchConstraint.new(name) unless constraint_exists?(name)
+      @app_module::Constraints.const_get(name)
+    end
+
+    def constraint_exists?(name)
+      @app_module.const_defined?(:Constraints) &&
+        @app_module::Constraints.const_defined?(name)
+    end
   end
 
   class ValidationError < RuntimeError; end
+  class NoSuchConstraint < RuntimeError; end
 
   module Util
     def self.underscore(string)

lib/raptor/router.rb

@@ -202,13 +202,13 @@ def custom_constraints
   end
 
   class Constraints
-    def initialize(app_module)
-      @app_module = app_module
+    def initialize(app)
+      @app = app
     end
 
     def matching(name)
-      constraint = @app_module::Constraints.const_get(Util.camel_case(name))
-      [constraint]
+      constraint = @app.constraint_named(Util.camel_case(name))
+      [constraint.new]
     end
   end
 

spec/app_spec.rb

@@ -61,6 +61,11 @@ module Fruit
         end
       end
 
+      module Constraints
+        class Never
+        end
+      end
+
       App = Raptor::App.new(self) do
       end
     end
@@ -99,5 +104,19 @@ module EmptySite
       app.injectables.should == []
     end
   end
+
+  describe "#constraint_named" do
+    it "has the named constraint" do
+      app = AwesomeSite::App
+      app.constraint_named(:Never).should == AwesomeSite::Constraints::Never
+    end
+
+    it "warns of missing constraints" do
+      app = EmptySite::App
+      expect do
+        app.constraint_named(:DoesNotExist)
+      end.to raise_error(Raptor::NoSuchConstraint)
+    end
+  end
 end