C++ Design Patterns

Educational implementations of GoF (Gang of Four) design patterns in modern C++20. Each pattern includes a practical example and a coding exercise from the Udemy C++ course.

Patterns Covered

Creational Patterns

Pattern	File	Description
SOLID Principles	solid.cpp	Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion
Builder	builder.cpp	Construct complex objects step by step
Factory	factory.cpp	Create objects without specifying exact class
Prototype	prototype.cpp	Clone existing objects
Singleton	singleton.cpp	Ensure only one instance exists

Structural Patterns

Pattern	File	Description
Adapter	adapter.cpp	Convert interface to another interface
Bridge	bridge.cpp	Separate abstraction from implementation
Composite	composite.cpp	Tree structures, part-whole hierarchies
Decorator	decorator.cpp	Add behavior dynamically without subclassing
Facade	facade.cpp	Simplified interface to complex subsystem
Flyweight	flyweight.cpp	Share common state between many objects
Proxy	proxy.cpp	Placeholder to control access to another object

Behavioral Patterns

Pattern	File	Description
Chain of Responsibility	chain_of_responsibility.cpp	Pass requests along a chain of handlers
Command	command.cpp	Encapsulate requests as objects, support undo/redo
Interpreter	interpreter.cpp	Evaluate language grammar with AST
Iterator	iterator.cpp	Traverse aggregate without exposing internals
Mediator	mediator.cpp	Central hub for component communication
Memento	memento.cpp	Capture and restore object state, undo/redo stacks
Observer	observer.cpp	Notify dependents of state changes automatically
State	state.cpp	Alter behavior when object's state changes
Strategy	strategy.cpp	Family of interchangeable algorithms
Template Method	template_method.cpp	Skeleton algorithm with customizable steps
Visitor	visitor.cpp	Double-dispatch operations on object structures

Build

mkdir -p build && cd build
cmake ..
cmake --build .

Run a Pattern

./build/singleton
./build/flyweight
./build/mediator
./build/command
./build/observer
./build/state
./build/strategy
./build/visitor

VS Code Debug Config

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "lldb",
            "request": "launch",
            "name": "Launch",
            "program": "${workspaceFolder}/build/udemy_1_initial",
            "args": [],
            "cwd": "${workspaceFolder}"
        }
    ]
}

Requirements

• CMake 3.10+
• C++20 compatible compiler (GCC 10+, Clang 12+, MSVC 2019+)

License

MIT