What is the problem?

• Adding a new type means changes to many files
• This can be error prone and complex
• Example

What is polymorphism

• Literally, many forms
• The same interface can be used to represent many classes
• Example

How can we use it make code changes faster?

Example

Step 1

Find switch

Step 2

Write tests

Step 3

Add classes

Step 4

Create factory

Step 5

Refactor and run tests

Key points

• Any time you see a switch statement, check if it could be replaced with polymorphism
• Uncle Bob: switch statements are only okay inside a factory

Pros and cons