At the end of 2017 I got into mobile apps programming. At that time I haven?t got much experience in OOP languages (I known mostly C) So It was heck of a journey! I have started by learning about MVC and storyboard. I followed some curse on UDEMY that supposedly should learn you "proper IOS programming", but I found it really rudimentary? It did not explained everything in details so I dropped It in favour of Stanford University course that was available for free on youtube at that time.
So my first app was basically a copy of the apple build in calculator. It has all the basic operations and even followed on proper order of math operations! Unfortunately it did not show more functions in landscape mode (see screenshot). Thankfully I managed to still compile this project after 4.5 years! I just had to migrate from Swift 3 (which is not supported in current version of Xcode an IOS) to Swift 5 and everything worked on iPhone 8 simulator. Well it was just a Calculator app so what could go wrong... But at that time I was really proud of It, I even made a custom icon for it! Best experience from this project was to learn a new language and programming paradigm.