id 1763525961

CMakeLists.txt

@@ -99,6 +99,7 @@ set(APP_SOURCES
     "src/patterns/structural/Facade.cpp"
     "src/patterns/structural/Decorator.cpp"
     "src/patterns/behavioral/ChainOfCommand.cpp"
+    "src/patterns/behavioral/Command.cpp"
 )
 
 # Test files

src/patterns/behavioral/ChainOfCommand.cpp

@@ -16,6 +16,9 @@ namespace
 {
     namespace CoR
     {
+        /*
+        *  Handler - defines an interface for handling requests
+        */
         class IHandler
         {
         public:
@@ -57,6 +60,10 @@ namespace
             }
         };
 
+        /**
+         * CoreteHandlers - handles the requests it is responsible for
+         * If it can handle the request it does so, otherwise it sends the request to its successor
+         */
         class ConcreteHandlerGET : public AbstractHandler
         {
         private:
@@ -116,6 +123,9 @@ namespace
             }
         };
 
+        /**
+         * Client - sends commands to the first object in the chain that may handle the command
+         */
         namespace Client
         {
             void clientCode(IHandler &handler, const std::string &request)
@@ -155,6 +165,7 @@ struct CoRAutoRunner
 {
     CoRAutoRunner()
     {
+        std::cout << "\n--- CoR Pattern Example ---\n";
         CoR::run();
     }
 };

src/patterns/behavioral/Command.cpp

@@ -0,0 +1,162 @@
+// Command is a behavioral design pattern that turns a request into a stand-alone object that contains all information about the request. (receivers, payloads)
+// This transformation lets you pass requests as a method arguments, delay or queue a request’s execution, and support undoable operations.
+// Allows an object to send a command without knowing what object will receive and handle it.
+// Appicability:
+// (*)   when you want to parameterize objects with operations.
+// (**)  when you want to queue operations, schedule their execution, or execute them remotely.
+// (***) when you want to implement reversible operations.
+
+// UML: docs/uml/patterns_behavioral_command.drawio.svg
+
+#include <iostream>
+#include <string>
+
+namespace
+{
+    namespace Command
+    {
+
+        /**
+         * The Command interface usually declares just a single method for executing the command.
+         * e.g. Save, Undo, Jump, Backup, CreateOrder
+         */
+        class ICommand
+        {
+        public:
+            virtual void execute() const = 0;
+        };
+
+        /**
+         * The Receiver class contains some business logic. Almost any object may act as a receiver.
+         * Most commands only handle the details of how a request is passed to the receiver, while the receiver itself does the actual work.
+         * e.g. Document, GameCharacter, DB service
+         */
+        class Receiver
+        {
+        public:
+            static void doCheck()
+            {
+                std::cout << "Receiver checking... \n";
+            };
+            static void doInit()
+            {
+                std::cout << "Receiver initializing... \n";
+            };
+            static void doLaunch(const std::string &arg)
+            {
+                std::cout << "Receiver launching... \n\t" << arg << "\n";
+            };
+        };
+
+        /**
+         * Concrete Commands implement various kinds of requests.
+         *  A concrete command isn’t supposed to perform the work on its own, but rather to pass the call to one of the business logic objects.
+         * However, for the sake of simplifying the code, these classes can be merged.
+         */
+        class SimpleConcreteCommand : public ICommand
+        {
+        public:
+            void execute() const override
+            {
+                std::cout << "\t SimpleCommand executed \n";
+            }
+        };
+
+        class ComplexConcreteCommand : public ICommand
+        {
+        private:
+            Receiver *m_receiver;
+            std::string m_payload;
+
+        public:
+            ComplexConcreteCommand(Receiver *receiver, const std::string &payload) : m_receiver{receiver}, m_payload{payload} {};
+
+            void execute() const override
+            {
+                std::cout << "\t ComplexCommand executed \n";
+                this->m_receiver->doCheck();
+                this->m_receiver->doInit();
+                this->m_receiver->doLaunch(m_payload);
+            }
+        };
+
+        /**
+         *The Sender class (aka invoker) is responsible for initiating requests.
+         *This class must have a field for storing a reference to a command object.
+         *The sender triggers that command instead of sending the request directly to the receiver.
+         *Note that the sender isn’t responsible for creating the command object. Usually, it gets a pre-created command from the client via the constructor.
+         *e.g. Button, Shortcut, Scheduler, Event bus...
+         */
+        class Invoker
+        {
+        private:
+            ICommand *m_on_start;
+            ICommand *m_on_finish;
+
+        public:
+            explicit Invoker(ICommand *s = nullptr, ICommand *f = nullptr) : m_on_start{s}, m_on_finish{s}
+            {
+            }
+
+            ~Invoker()
+            {
+                delete m_on_start;
+                delete m_on_finish;
+            }
+
+            void setOnStart(ICommand *command)
+            {
+                this->m_on_start = command;
+            }
+
+            void setOnFinish(ICommand *command)
+            {
+                this->m_on_finish = command;
+            }
+
+            void invoke() const
+            {
+                if (m_on_start != nullptr)
+                {
+                    m_on_start->execute();
+                }
+
+                if (m_on_finish != nullptr)
+                {
+                    m_on_finish->execute();
+                }
+            }
+        };
+
+        namespace Client
+        {
+            void clientCode(const Invoker *invoker)
+            {
+                invoker->invoke();
+            }
+
+        }
+
+        void run()
+        {
+            Receiver *ui = new Receiver();
+            // How to execute these command when something triggered
+            Invoker *invoker = new Invoker();
+            invoker->setOnStart(new SimpleConcreteCommand());
+            invoker->setOnFinish(new ComplexConcreteCommand(ui, "cmd --version"));
+            Client::clientCode(invoker);
+            delete ui;
+        }
+    }
+}
+
+struct CommandAutoRunner
+{
+    CommandAutoRunner()
+    {
+        std::cout << "\n--- Command Pattern Example ---\n";
+        Command::run();
+    }
+};
+
+static CommandAutoRunner instance;