Factory method pattern
part 4/15 · 25.1 KB total
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Structure
UML class diagram
In the above UML class diagram, the Creator class that requires a Product object does not instantiate the Product1 class directly. Instead, the Creator refers to a separate factoryMethod() to create a product object, which makes the Creator independent of the exact concrete class that is instantiated. Subclasses of Creator can redefine which class to instantiate. In this example, the Creator1 subclass implements the abstract factoryMethod() by instantiating the Product1 class.
Examples
This C++23 implementation is based on the pre C++98 implementation in the Design Patterns book.cite-ref-footnotegammahelmjohnsonvlissides1995122-5-0[5]
import std;
enum class ProductId {MINE, YOURS};
// defines the interface of objects the factory method creates.
class Product {
public:
virtual void print() = 0;
virtual ~Product() = default;
};
// implements the Product interface.
class ConcreteProductMINE: public Product {
public:
void print() {
std::println("this={} print MINE", this);
}
};
// implements the Product interface.
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