Is there no input() function in Swift? No. Not for now. But how then can we enter a number or a string from the command line interface (CLI)?
1. Copy this function to your code:
func input() -> String {
var keyboard = NSFileHandle.fileHandleWithStandardInput()
var inputData = keyboard.availableData
var strData = NSString(data: inputData, encoding: NSUTF8StringEncoding)!
return strData.stringByTrimmingCharactersInSet(NSCharacterSet.newlineCharacterSet())
}
2. Use it like so:
print("Enter number: ")
let n_str = input() // NOTE: n_str is an Optional (type), this means String or nothing
let n = n_str.toInt()! // NOTE: ! "unpacks" the Optional type n_str
3. Testing: What happens, if I enter a Number:
Enter number: 12
Result: Just seems to work
4. Testing: What happens if I just enter ENTER:
Enter number: // <--- I just hit ENTER here
fatal error: unexpectedly found nil while unwrapping an Optional value 0 swift 0x00000001039d82b8 llvm::sys::PrintStackTrace(__sFILE*) + 40 1 swift 0x00000001039d8794 SignalHandler(int) + 452 [...]
Result: It crashes, which is better then continue with undefined values
5. Testing: What happens if I just enter a string not a number:
Enter Number: abc
fatal error: unexpectedly found nil while unwrapping an Optional value 0 swift 0x000000010bc512b8 llvm::sys::PrintStackTrace(__sFILE*) + 40 1 swift 0x000000010bc51794 SignalHandler(int) + 452 [...]
Result: It does crash, witch is better then continue with undefined values!
6. Conclusion
So, sometimes it's a better your program crashes then just go ahead somehow undefined as it's possible with plain C for example.
Missing Swift Computer Language Feature: But really, Swift should and has to include an input() function by default. Apple, if you read this, just do it 😉 Swift seems to be a great new computer language and I start to really like it.
