Factory Method

Factory method is a creational design pattern which solves the problem of creating product objects without specifying their concrete classes. This pattern defines a method, which should be used for creating objects instead of direct constructor call (new operator). Subclasses can override this method to change the class of objects that will be created.

With that, you can override the factory method in a subclass and change the class of products (products are th objects returned by a factory method) being created by the method.

There's a slight limitation though: subclasses may return different types of products only if these products have a common base class or interface. Also, the factory method in the base class should have its return type declared as this interface.

For example, both AWSStorageClient and GoogleStorageClient classes should implement the Client interface which declares a method called upload. Each class implements this method differently: aws upload to aws cloud, google deliver google cloud. The factory method in the AWSStorage class returns AWSStorageClient objects, whereas the factory method in the GoogleStorage class returns GoogleStorageClient.

The code that uses the factory method (runLogic) doesn’t see a difference between the actual products returned by various subclasses. The runLogic treats all the products as abstract Client. The runLogic knows that all Client objects are supposed to have the upload method, but exactly how it works isn’t important to the runLogic.

This project was based on the article: Factory Method from Refactoring Guru, click here to see the source.

🧙 Why

The main file is src/main/app.ts, this file has three methods: main() that call bootstrap() and runLogic().

bootstrap() method assigns the class' attribute private storage: Storage with one Storage depending of const TYPE_STORAGE.

runLogic() call the method uploadFile(path) of the assigned storage.

⌨️ Basic Usage

npm install
npm start

📜 Run tests

npm test

📋 Contributing Guide

I welcome all pull requests. Please make sure you add appropriate test cases for any features added. Before opening a PR please make sure to run the following scripts:

• npm run lint checks for code errors and format according to gof-factory-method-nodejs
• npm test make sure all tests pass
• npm test -- --coverage make sure the coverage has not decreased from current master