POP encourages us to develop protocols and extend them instead of classes and inheritance. POP is new in the Objective-C and Swift development community, but what it provides is not very different from the concept of Abstract classes in languages such as Java and C#, and pure-virtual functions in C++.

In Swift, classes, structs, and enumerations can conform to protocols. This makes protocols more usable because inheritance does not work for structs and enumerations.