From 81e9ed7fdd65ca4816ac6a76139d6c18d5182a21 Mon Sep 17 00:00:00 2001
From: Ivo van Dongen <info@ivovandongen.nl>
Date: Fri, 21 Jul 2017 11:26:40 +0300
Subject: [core] add ask pattern to actor ref

---
 include/mbgl/actor/actor_ref.hpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

(limited to 'include')

diff --git a/include/mbgl/actor/actor_ref.hpp b/include/mbgl/actor/actor_ref.hpp
index aeb5bb4507..958ee3777c 100644
--- a/include/mbgl/actor/actor_ref.hpp
+++ b/include/mbgl/actor/actor_ref.hpp
@@ -35,6 +35,27 @@ public:
         }
     }
 
+    template <typename Fn, class... Args>
+    auto ask(Fn fn, Args&&... args) {
+        // Result type is deduced from the function's return type
+        using ResultType = typename std::result_of<decltype(fn)(Object, Args...)>::type;
+
+        std::promise<ResultType> promise;
+        auto future = promise.get_future();
+
+        if (auto mailbox = weakMailbox.lock()) {
+            mailbox->push(
+                    actor::makeMessage(
+                            std::move(promise), *object, fn, std::forward<Args>(args)...
+                    )
+            );
+        } else {
+            promise.set_exception(std::make_exception_ptr(std::runtime_error("Actor has gone away")));
+        }
+
+        return future;
+    }
+
 private:
     Object* object;
     std::weak_ptr<Mailbox> weakMailbox;
-- 
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