implement a simple path param binder

Former-commit-id: 2edc7f115332b7afe42d6b0b1b7b6edd4a44a121

mvc2/path_param.go

@@ -0,0 +1,44 @@
+package mvc2
+
+import (
+	"github.com/kataras/iris/context"
+	"github.com/kataras/iris/core/memstore"
+)
+
+// PathParams is the context's named path parameters, see `PathParamsBinder` too.
+type PathParams = context.RequestParams
+
+// PathParamsBinder is the binder which will bind the `PathParams` type value to the specific
+// handler's input argument, see `PathParams` as well.
+func PathParamsBinder(ctx context.Context) PathParams {
+	return *ctx.Params()
+}
+
+// PathParam describes a named path parameter, it's the result of the PathParamBinder and the expected
+// handler func's input argument's type, see `PathParamBinder` too.
+type PathParam struct {
+	memstore.Entry
+	Empty bool
+}
+
+// PathParamBinder is the binder which binds a handler func's input argument to a named path parameter
+// based on its name, see `PathParam` as well.
+func PathParamBinder(name string) func(ctx context.Context) PathParam {
+	return func(ctx context.Context) PathParam {
+		e, found := ctx.Params().GetEntry(name)
+		if !found {
+
+			// useless check here but it doesn't hurt,
+			// useful only when white-box tests run.
+			if ctx.Application() != nil {
+				ctx.Application().Logger().Warnf(ctx.HandlerName()+": expected parameter name '%s' to be described in the route's path in order to be received by the `ParamBinder`, please fix it.\n The main handler will not be executed for your own protection.", name)
+			}
+
+			ctx.StopExecution()
+			return PathParam{
+				Empty: true,
+			}
+		}
+		return PathParam{e, false}
+	}
+}