How to refactor code

Refactoring: Change the code's structure without changing its external behavior

• Low coupling: Separate all that's possible to separate without making a mess
• High cohesion: Minimize the mess ~ Minimize the inter-group dependencies and maximize the intra-group ones

Invariants:

• Behavior must be the same at all times - i.e Testing
• Optionally format at all times
• Optionally 1 class per file

Procedure:

1. Divide / Decompose
2. Group / Abstract
3. Join / Compose

Incremental version (OOP)

• Minimal piece of abstraction = Method

• Group of methods = Class

• Group of classes = Module

• Use testing at all times

Method level:

1. Extract all possible methods
2. Group methods into other methods
3. Compose methods

Method-Class level:

1. Divide methods
2. Group methods into classes
3. Compose classes

Class level:

1. Extract classes
2. Group classes into other classes
3. Compose classes

Class-Module level:

1. Divide classes
2. Group classes into modules
3. Compose modules