simple-factory

Simple Factory Pattern

Intent

Creates objects without exposing the instantiation logic to the client.

Applicability

Use the Simple Factory pattern when

• you want to provide a class library of products, and you want to reveal just their interfaces, not their implementations.
• a system should be independent of how its products are created, composed, and represented.

Structure

Participants

• SimpleFactory
  • define a static factory method to create concrete product objects.
• Product
  • defines the interface of objects the static factory method creates.
• ConcreteProduct
  • implements the Product interface.
• Client
  • creates a new object using simple factory.

Example

Imagine you are creating a calculator. You want to execute different operations according to operator(+,-,*,/), which means you need create different concrete operations according to different operator. This example demonstrates how to achieve it.

Participants in this example:

• Operation's companion object is the SimpleFactory, and the apply() function is the static factory method.
• Operation is the Prodcut.
• AddOperation/SubOperation/MulOperation/DivOperation is the ConcreteProduct.
• App is the Client.

Scala Tips

• in scala, the apply function of companion object is the best place to implement the static factory method of simple factory.

Reference