Merge pull request #76 from ayaankhan98/master

recieve response without request being another argument in handler

docs/guides/routes.md

@@ -30,8 +30,7 @@ You can also access the url parameters in the handler using `#!cpp req.url_param
 For more information on `crow::request` go [here](../../reference/structcrow_1_1request.html).<br><br>
 
 ###Response
-Crow also provides the ability to define a response in the parameters by using `#!cpp ([](const crow::request& req, crow::response& res){...})`.<br>
+Crow also provides the ability to define a response in the parameters by using `#!cpp ([](crow::response& res){...})`.<br><br>
-If you don't want to use the request you can write `#!cpp ([](const crow::request& , crow::response& res){...})`.<br><br>
 
 Please note that in order to return a response defined as a parameter you'll need to use `res.end();`.<br><br>
 

examples/example.cpp

@@ -13,12 +13,11 @@ struct ExampleMiddleware
 {
     std::string message;
 
-    ExampleMiddleware() 
+    ExampleMiddleware() : message("foo")
     {
-        message = "foo";
     }
 
-    void setMessage(std::string newMsg)
+    void setMessage(const std::string &newMsg)
     {
         message = newMsg;
     }
@@ -84,7 +83,7 @@ int main()
 
     // To see it in action submit {ip}:18080/add/1/2 and you should receive 3 (exciting, isn't it)
     CROW_ROUTE(app,"/add/<int>/<int>")
-    ([](const crow::request& /*req*/, crow::response& res, int a, int b){
+    ([](crow::response& res, int a, int b){
         std::ostringstream os;
         os << a+b;
         res.write(os.str());

examples/example_vs.cpp

@@ -13,12 +13,11 @@ struct ExampleMiddleware
 {
     std::string message;
 
-    ExampleMiddleware() 
+    ExampleMiddleware() : message("foo")
     {
-        message = "foo";
     }
 
-    void setMessage(std::string newMsg)
+    void setMessage(const std::string &newMsg)
     {
         message = newMsg;
     }
@@ -78,7 +77,7 @@ int main()
     });
 
     app.route_dynamic("/add/<int>/<int>")
-    ([](const crow::request& req, crow::response& res, int a, int b){
+    ([](crow::response& res, int a, int b){
         std::ostringstream os;
         os << a+b;
         res.write(os.str());

examples/example_with_all.cpp

@@ -41,8 +41,10 @@ int main()
         return crow::response(os.str());
     });
 
+    // example which uses only response as a paramter wihtout
+    // request being a parameter.
     CROW_ROUTE(app,"/add/<int>/<int>")
-    ([](const crow::request& /*req*/, crow::response& res, int a, int b){
+    ([](crow::response& res, int a, int b){
         std::ostringstream os;
         os << a+b;
         res.write(os.str());

include/crow/routing.h

@@ -529,7 +529,33 @@ namespace crow
         template <typename Func>
         typename std::enable_if<
             !black_magic::CallHelper<Func, black_magic::S<Args...>>::value &&
-            !black_magic::CallHelper<Func, black_magic::S<crow::request, Args...>>::value,
+            !black_magic::CallHelper<Func, black_magic::S<crow::request, Args...>>::value &&
+            black_magic::CallHelper<Func, black_magic::S<crow::response&, Args...>>::value,
+        void>::type
+        operator()(Func&& f)
+        {
+          static_assert(black_magic::CallHelper<Func, black_magic::S<Args...>>::value ||
+              black_magic::CallHelper<Func, black_magic::S<crow::response&, Args...>>::value
+              ,
+              "Handler type is mismatched with URL parameters");
+          static_assert(std::is_same<void, decltype(f(std::declval<crow::response&>(), std::declval<Args>()...))>::value,
+                        "Handler function with response argument should have void return type");
+          handler_ = (
+#ifdef CROW_CAN_USE_CPP14
+                [f = std::move(f)]
+#else
+                [f]
+#endif
+                (const crow::request&, crow::response& res, Args ... args){
+                  f(res, args...);
+                });
+        }
+
+        template <typename Func>
+        typename std::enable_if<
+            !black_magic::CallHelper<Func, black_magic::S<Args...>>::value &&
+            !black_magic::CallHelper<Func, black_magic::S<crow::request, Args...>>::value &&
+            !black_magic::CallHelper<Func, black_magic::S<crow::response&, Args...>>::value,
             void>::type
         operator()(Func&& f)
         {