Swift is a new programming language for iOS, macOS, watchOS, and tvOS app development.
It has a clean and modern syntax, offers seamless access to existing C and Objective-C code and frameworks, and is memory safe by default.
Memory safety is the state of being protected from various software bugs and security vulnerabilities when dealing with memory access, such as buffer overflows and dangling pointers.
Wikipedia
Compiled
struct x class
Access control
Property observers
Automatic Reference Counting
Enums
Protocol
Function Argument Labels and Parameter Names
strong x weak
“Use a weak reference whenever it is valid for that reference to become nil at some point during its lifetime. Conversely, use an unowned reference when you know that the reference will never be nil once it has been set during initialization.”
Apple Documentation
Error handling
Optional
If let x guard let
Extension
Closure aka () => {}