Use StrCat to do efficient joining. (#438)

modules/dreamview/backend/common/dreamview_gflags.cc

@@ -36,4 +36,5 @@ DEFINE_bool(
 DEFINE_string(routing_result_file, "modules/map/data/garage_routing.pb.txt",
               "File path of the routing result that SimControl will read the "
               "start point from. If this is absent, SimControl will directly "
-              "take the RoutingResponse from ROS to determine the start point.");
+              "take the RoutingResponse from ROS to determine the start "
+              "point.");

modules/dreamview/backend/map/map_service.cc

@@ -18,6 +18,8 @@
 
 #include <algorithm>
 
+#include "modules/common/util/string_util.h"
+
 namespace apollo {
 namespace dreamview {
 
@@ -94,14 +96,14 @@ MapElementIds::MapElementIds(const nlohmann::json &json_object)
 
 size_t MapElementIds::Hash() const {
   static std::hash<std::string> hash_function;
-  std::string text;
-  text = std::accumulate(lane.begin(), lane.end(), text);
-  text = std::accumulate(crosswalk.begin(), crosswalk.end(), text);
-  text = std::accumulate(junction.begin(), junction.end(), text);
-  text = std::accumulate(signal.begin(), signal.end(), text);
-  text = std::accumulate(stop_sign.begin(), stop_sign.end(), text);
-  text = std::accumulate(yield.begin(), yield.end(), text);
-  text = std::accumulate(overlap.begin(), overlap.end(), text);
+  const std::string text = apollo::common::util::StrCat(
+      apollo::common::util::PrintIter(lane, ""),
+      apollo::common::util::PrintIter(crosswalk, ""),
+      apollo::common::util::PrintIter(junction, ""),
+      apollo::common::util::PrintIter(signal, ""),
+      apollo::common::util::PrintIter(stop_sign, ""),
+      apollo::common::util::PrintIter(yield, ""),
+      apollo::common::util::PrintIter(overlap, ""));
   return hash_function(text);
 }
 

modules/dreamview/backend/sim_control/sim_control.cc

@@ -81,7 +81,8 @@ void SimControl::Start() {
   if (initial_start_) {
     // Setup planning and routing result data callback.
     AdapterManager::AddPlanningCallback(&SimControl::OnPlanning, this);
-    AdapterManager::AddRoutingResponseCallback(&SimControl::SetStartPoint, this);
+    AdapterManager::AddRoutingResponseCallback(&SimControl::SetStartPoint,
+                                               this);
 
     // Start timer to publish localiztion and chassis messages.
     sim_control_timer_ = AdapterManager::CreateTimer(

modules/dreamview/backend/simulation_world/simulation_world_service.h

@@ -51,8 +51,6 @@ namespace dreamview {
  */
 class SimulationWorldService {
  public:
-  using Json = nlohmann::json;
-
   // The maximum number of monitor message items to be kept in
   // SimulationWorld.
   static constexpr int kMaxMonitorItems = 30;
@@ -79,7 +77,7 @@ class SimulationWorldService {
    * @brief Returns the json representation of the SimulationWorld object.
    * @return Json object equivalence of the SimulationWorld object.
    */
-  Json GetUpdateAsJson() const;
+  nlohmann::json GetUpdateAsJson() const;
 
   /**
    * @brief The function Update() is periodically called to check for updates