You are amazing, my code like a kid toy nearby you code XD

but if i wanna check number with sign?:) Where's your test?

bang bang

Great kata. The only thing I would suggest is that it be updated from Swift 3.1.1 to at least Swift 4 especially with Swift 5 lurking around the corner. Thank you for all of your effort.

'characters' is deprecated now !
How will it be in swift4 ?

No random tests

Base conversion is a duplicate to many existing katas.

It's a bit weird that the function should return "" when the input is empty, and throw when the input contains invalid characters. Can't you just have the function return an optional, and have us return nil if the input is invalid, no matter the reason?

Thank you! I've updated kata, reflecting suggestion from you comment.
It should now throw an exception when either the string is not in the base from or string includes characters that are outside of 0->Z scope.

What should we do when string is not in base from?

Example:

convert(string: "312DASD", from: 13, to: 4)
// D >= 13, S >= 13