Add templatemethod pattern

Author: urbytes21

CMakeLists.txt

@@ -104,6 +104,7 @@ set(APP_SOURCES
     "src/patterns/behavioral/Mediator.cpp"
     "src/patterns/behavioral/Memento.cpp"
     "src/patterns/behavioral/Visitor.cpp"
+    "src/patterns/behavioral/TemplateMethod.cpp"
 )
 
 # Test files

docs/uml/pattern_behavioral_templatemethod.drawio.svg

@@ -0,0 +1,125 @@
+// cppcheck-suppress-file [functionStatic]
+
+//  is a behavioral design pattern that defines the skeleton of an algorithm in the `superclass`
+// but lets `subclasses` override specific steps of the algorithm without changing its structure.
+// Appicability:
+// (*)    when you want to let clients extend only particular steps of an algorithm, but not the whole algorithm or its structure.
+// (**)   when you have several classes that contain almost identical algorithms with some minor differences.
+//        As a result, you might need to modify all classes when the algorithm changes.
+// (**)  when a behavior makes sense only in some classes of a class hierarchy, but not in others.
+// UML: docs/uml/patterns_behavioral_visitor.drawio.svg
+
+#include <iostream>
+#include <string>
+#include <vector>
+
+namespace
+{
+    namespace TemplateMethod
+    {
+        class AbstractClass
+        {
+        public:
+            virtual ~AbstractClass() = default;
+            // Template Method (non-virtual => cannot be overridden)
+            // Defines the algorithm's skeleton and ensures subclasses cannot change the flow.
+            void templateMethod() const
+            {
+                baseOperation1();
+                abstractMethod1();
+                hookOperation1();
+
+                baseOperation2();
+                abstractMethod2();
+                hookOperation2();
+            }
+
+        protected:
+            // 1. Base operations: These have full implementations and cannot be overridden.
+            void baseOperation1() const
+            {
+                // Common logic step 1
+                std::cout << "[AbstractClass]\t Executed base operation - 1\n";
+            }
+
+            void baseOperation2() const
+            {
+                // Common logic step 2
+                std::cout << "[AbstractClass]\t Executed base operation - 2\n";
+            }
+
+            // 2. Hook methods: Subclasses may override them to extend behavior, but overriding is optional.
+            virtual void hookOperation1() const {}
+            virtual void hookOperation2() const {}
+
+            // 3. Abstract methods: Subclasses MUST provide implementations.
+            virtual void abstractMethod1() const = 0;
+            virtual void abstractMethod2() const = 0;
+        };
+
+        class ConcreteClass1 : public AbstractClass
+        {
+        public:
+            void abstractMethod1() const override
+            {
+                std::cout << "[ConcreteClass1]\t Implemented Operation - 2\n";
+            }
+
+            void abstractMethod2() const override
+            {
+                std::cout << "[ConcreteClass1]\t Implemented Operation - 2\n";
+            }
+
+            void hookOperation1() const override
+            {
+                std::cout << "[ConcreteClass1]\t Overridden Hook - 1\n";
+            }
+        };
+
+        class ConcreteClass2 : public AbstractClass
+        {
+        public:
+            void abstractMethod1() const override
+            {
+                std::cout << "[ConcreteClass2]\t Implemented Operation - 2\n";
+            }
+
+            void abstractMethod2() const override
+            {
+                std::cout << "[ConcreteClass2]\t Implemented Operation - 2\n";
+            }
+        };
+
+        namespace Client
+        {
+            void clientCode(const AbstractClass *clazz)
+            {
+                clazz->templateMethod();
+            }
+        }
+        void run()
+        {
+            std::cout << "\t[ConcreteClass1] Executed templateMethod\n";
+            AbstractClass *clazz1 = new ConcreteClass1();
+            Client::clientCode(clazz1);
+
+            std::cout << "\t[ConcreteClass1] Executed templateMethod\n";
+            AbstractClass *clazz2 = new ConcreteClass2();
+            Client::clientCode(clazz2);
+
+            delete clazz1;
+            delete clazz2;
+        }
+    }
+}
+
+struct TemplateMethodAutoRunner
+{
+    TemplateMethodAutoRunner()
+    {
+        std::cout << "\n--- TemplateMethod Pattern Example ---\n";
+        TemplateMethod::run();
+    }
+};
+
+static TemplateMethodAutoRunner instance;