From 5ee05a7781396004cb617002b6cbe8b7402616a6 Mon Sep 17 00:00:00 2001
From: Ivo van Dongen <info@ivovandongen.nl>
Date: Fri, 21 Jul 2017 12:32:13 +0300
Subject: [core] make actor self reference optional

---
 include/mbgl/actor/actor.hpp | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

(limited to 'include')

diff --git a/include/mbgl/actor/actor.hpp b/include/mbgl/actor/actor.hpp
index 00e1bb82f8..74d5a66285 100644
--- a/include/mbgl/actor/actor.hpp
+++ b/include/mbgl/actor/actor.hpp
@@ -7,6 +7,7 @@
 
 #include <memory>
 #include <future>
+#include <type_traits>
 
 namespace mbgl {
 
@@ -47,10 +48,21 @@ namespace mbgl {
 template <class Object>
 class Actor : public util::noncopyable {
 public:
-    template <class... Args>
+
+    // Enabled for Objects with a constructor taking ActorRef<Object> as the first parameter
+    template <typename U = Object, class... Args,
+            typename std::enable_if<std::is_constructible<U, ActorRef<Object>, Args...>::value>::type...>
+    Actor(Scheduler& scheduler, Args&&... args_)
+            : mailbox(std::make_shared<Mailbox>(scheduler)),
+              object(self(), std::forward<Args>(args_)...) {
+    }
+
+    // Enabled for plain Objects
+    template <typename U = Object, class... Args,
+            typename std::enable_if<!std::is_constructible<U, ActorRef<Object>, Args...>::value>::type...>
     Actor(Scheduler& scheduler, Args&&... args_)
-        : mailbox(std::make_shared<Mailbox>(scheduler)),
-          object(self(), std::forward<Args>(args_)...) {
+            : mailbox(std::make_shared<Mailbox>(scheduler)),
+              object(std::forward<Args>(args_)...) {
     }
 
     ~Actor() {
-- 
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