Swift Rounding up Double
There is a built-in global function called ceil which does exactly this:
var numberOfBottles = ceil(totalVolume/volumeEachBottles)This returns 2, as a Double.
ceil is actually declared in math.h and documented here in the OS X man pages. It is almost certainly more efficient than any other approach.
Even if you need an Int as your final result, I would start by calculating ceil like this, and then using the Int constructor on the result of the ceil calculation.