##Angular - one library used by 4 different web apps - polymorphism example

Description: Shareable-lib is a library shared between 4 different web projects (for the needs of this tutorial, named webApp1, webApp2, webApp3 and webApp4).

What shareable library does - it provides authentication service and user context service, but each of them only in one, default version. User context service has dependency of authentication service (injected in constructor). Some web apps want to use the default versions of services, but others would like to use eg. only default version of user context service, and implemenent it's custom authentication service .

How the needs of each web app look like:

1. WebApp1:

• would like to use default user context service
• is happy with default authentication service

2. WebApp2:

• would like to use different user context service, default one does not suit it
• is happy with default authentication service

3. WebApp3:

• would like to use default user context service
• default authentication service does not suit it needs, it would like to use custom implementation

4. WebApp4:

• likes default user context service, but there are small bits missing - so it uses composition pattern to create it's own implementation
• likes also default authentication service, but there are also small bits missing - as with user context service, this web app is using composition to overcome this problem

Implementation shows how the problem was solved using polymorphism.

How to run examples:

• npm install
• npm run serve-all

To access each webapp, go to:

• localhost:4201 to access webApp1
• localhost:4202 to access webApp2
• localhost:4203 to access webApp3
• localhost:4204 to access webApp4