Lære Flexible Object Creation with Factory Method

The Factory Method pattern is a fundamental creational design pattern that enables you to create objects without specifying the exact class of the object that will be created. By defining an interface for creating an object, but letting subclasses decide which class to instantiate, you gain flexibility and extensibility in your code. This approach is especially useful when your application must work with objects that share a common interface but may require different concrete implementations depending on context or configuration. Using Factory Method, you can decouple the client code from the concrete classes, making your codebase easier to maintain and extend as new requirements emerge.

ShapeFactory.h

Shape.h

Square.h

Circle.h


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class ShapeFactory {
public:
    static std::unique_ptr<Shape> createShape(const std::string& type)
    {
        if (type == "circle") return std::make_unique<Circle>();
        if (type == "square") return std::make_unique<Square>();
        return nullptr;
    }
};

The Factory Method pattern is a powerful way to support the open/closed principle, which states that software entities should be open for extension but closed for modification. When you use a factory, you can add new types of objects such as new shapes by introducing new classes and updating the factory logic, without changing the code that uses the factory. This minimizes the risk of introducing bugs into existing functionality and makes it easy to scale your application as new requirements arise. The client code remains unchanged and relies only on the abstract interface, while the factory encapsulates the logic for creating the appropriate concrete objects.

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