With Swift2 Apple introduced the protocol-oriented programming paradigm and this approach might help you in many ways during your development journey, why not use it in the data layer? Developing a flexible data layer could be challenging and hard to maintain. Changing data layer technology is not an unusual ask like moving from Core Data to Realm. We will use protocol-oriented programming to create an awesome data layer (data providers) that can be modified and replaced smoothly. You will be acquainted with micro-functional data providers. In the end, we will go through how to test our data layer and data providers.