Understanding Uncle Bob’s Principles of Object-Oriented Design (which resulted in the SOLID principles) is super important to really grasp the use of design patterns (like MVVM) and architectural patterns (like VIPER). It’s like the grammar for crafting proper object-oriented software.
And now here’s the good news: there is a Swift playground (and Markdown file to read online) that illustrates all the principles by Uncle Bob: The Principles of OOD in Swift 2.2
Check it out, take notes, and keep the principles close to your heart. They may save your life someday.