A friend sent me this in the morning:

“By convention, type names such as String or Int (or Dog or Cat) start with a capital letter; variable names start with a small letter. Do not violate this convention. If you do, your code might still compile and run just fine, but I will personally send agents to your house to remove your kneecaps in the dead of night.”

Excerpt From: Matt Neuburg. “iOS 10 Programming Fundamentals with Swift.” iBooks.