use shared ptr, makr fn const

subscriber-notifs/include/core/subscribable.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <memory>
 #include <unordered_map>
 #include <vector>
 
@@ -10,14 +11,17 @@ class Subscribable {
     using TSubscriber = Subscriber<TEventId, TEventInfo>;
 
    private:
-    std::unordered_map<TEventId, std::vector<TSubscriber*>> subscribersMap_;
+    std::unordered_map<TEventId, std::vector<std::shared_ptr<TSubscriber>>>
+        subscribersMap_;
 
    public:
-    void subscribe(const TEventId& eventId, TSubscriber* subscriber) {
+    void subscribe(const TEventId& eventId,
+                   std::shared_ptr<TSubscriber> subscriber) {
         subscribersMap_[eventId].push_back(subscriber);
     }
 
-    void unsubscribe(const TEventId& eventId, TSubscriber* subscriber) {
+    void unsubscribe(const TEventId& eventId,
+                     std::shared_ptr<TSubscriber> subscriber) {
         auto entry = subscribersMap_.find(eventId);
         if (entry == subscribersMap_.end()) {
             return;
@@ -29,13 +33,13 @@ class Subscribable {
         }
     }
 
-    void notify(const TEventId& eventId, const TEventInfo& eventInfo) {
+    void notify(const TEventId& eventId, const TEventInfo& eventInfo) const {
         auto entry = subscribersMap_.find(eventId);
         if (entry == subscribersMap_.end()) {
             return;
         }
 
-        for (TSubscriber* subscriber : entry->second) {
+        for (auto& subscriber : entry->second) {
             subscriber->onNotification(eventId, eventInfo);
         }
     }

subscriber-notifs/src/app/inventory_manager.cpp

@@ -2,6 +2,9 @@
 
 void InventoryManager::setInventory(const ProductId& productId,
                                     ProductCount quantity) {
+    ProductCount oldQuantity = inventory_[productId];
     inventory_[productId] = quantity;
-    this->notify(productId, quantity);
+    if (oldQuantity != quantity) {
+        this->notify(productId, quantity);
+    }
 }

subscriber-notifs/src/main.cpp

@@ -1,16 +1,18 @@
+#include <memory>
+
 #include "app/inventory_manager.hpp"
 #include "app/services.hpp"
 
 int main() {
     InventoryManager inventoryManager;
 
-    SmsService smsService;
-    EmailService emailService;
-    LogService logService;
+    auto smsService = std::make_shared<SmsService>();
+    auto emailService = std::make_shared<EmailService>();
+    auto logService = std::make_shared<LogService>();
 
-    inventoryManager.subscribe("ProductA", &smsService);
-    inventoryManager.subscribe("ProductB", &emailService);
-    inventoryManager.subscribe("ProductA", &logService);
+    inventoryManager.subscribe("ProductA", smsService);
+    inventoryManager.subscribe("ProductB", emailService);
+    inventoryManager.subscribe("ProductA", logService);
 
     inventoryManager.setInventory("ProductA", 100);
     inventoryManager.setInventory("ProductB", 200);