This is a Swift/Objective-C ouroboros.
An ouroboros is a type of quine where the programs will print each other in a loop - in this case, the Swift code prints the Objective-C program, and the Objective-C program in turn prints the Swift program. They can loop forever, producing exactly the same source code for each other.
I wrote this as a celebration of Swift 3 being officially released, since these are two languages that are near and dear to my heart. I hope you enjoy it!
##How to use this:
swift ouroboros.swift to obtain the Objective-C code.
Compile the Objective-C source with this command
clang -fobjc-arc -F/System/Library/Frameworks ouroboros.m -o objc_ouroboros
then run it like this to obtain the Swift code
###Writing to File from Command Line
You can redirect the output of a program into a file like this
swift ouroboros.swift > ouroboros.m
./objc_ouroboros > ouroboros.swift