Factory Method

Separates object (product) creation from usage in the main class (creator). The creation of the object is done in the superclass but allows the subclass to alter the type of objects to be created.

@startuml
Creator --right> Product
Creator <|-- ConcreteCreatorA
Creator <|-- ConcreteCreatorB
Product <|-- ConcreteProductA
Product <|-- ConcreteProductB

abstract Creator {
  ...
  useProduct()
  {abstract} createProduct(): Product
}
note left of Creator::useProduct
  product = createProduct()
  product.doSomething()
end note

note left of Creator::createProduct
  Factory method
end note

interface Product {
  doSomething()
}

class ConcreteCreatorA {
  createProduct(): Product
}
note right of ConcreteCreatorA::createProduct
  return ConcreteProductA()
end note

class ConcreteCreatorB {
  createProduct(): Product
}
@enduml

Usage

The separation of creation and usage is the core purpose of the factory method. Therefore, the advantages are:

• New product types are created from implementing the product and subclassing the creator.

• Allow external users to extend both usage and product types a la above