CoroutineStarter. keep(...) method to keep vars.

src/oatpp/core/async/Coroutine.cpp

@@ -249,8 +249,6 @@ Action CoroutineHandle::takeAction(Action&& action) {
       }
 
       case Action::TYPE_FINISH: {
-        /* Please note that savedCP->m_parentReturnAction should not be "REPEAT nor WAIT_RETRY" */
-        /* as funtion pointer (FP) is invalidated */
         action = std::move(_CP->m_parentReturnAction);
         AbstractCoroutine* savedCP = _CP;
         _FP = _CP->m_parentReturnFP;

src/oatpp/core/async/Coroutine.hpp

@@ -389,6 +389,16 @@ public:
    */
   CoroutineStarter& next(CoroutineStarter&& starter);
 
+  /**
+   * Keep variables for the time coroutine pipeline is executed. <br>
+   * Example usage is to keep shared_ptr to an object which calls coroutine.
+   * @tparam Args
+   * @param vars
+   * @return - this starter.
+   */
+  template<typename ... Args>
+  CoroutineStarter& keep(const Args&... vars);
+
 };
 
 /**
@@ -631,6 +641,28 @@ public:
   
 };
 
+template<typename ... Args>
+CoroutineStarter& CoroutineStarter::keep(const Args&... vars) {
+
+  class KeeperCoroutine : public Coroutine<KeeperCoroutine> {
+  private:
+    std::tuple<Args...> m_vars;
+  public:
+
+    KeeperCoroutine(const Args&... vars)
+      : m_vars(std::make_tuple(vars...))
+    {}
+
+    Action act() override {
+      return this->finish();
+    }
+
+  };
+
+  return next(KeeperCoroutine::start(vars...));
+
+}
+
 /**
  * Abstract coroutine with result.
  */