How do I take a substring to the first index of a character?

Question

I\'m very new to Swift; I\'ve spent the morning reading StackOverflow and trying many strategies, in vain, to accomplish the following:

I have a string, say \"12345 is

Answer 1

With Swift 5 you can use:

myStr.prefix(upTo: myStr.firstIndex(of: " ") ?? myStr.startIndex)

You may need to cast it back to String (String(myStr.prefix(upTo: myStr.firstIndex(of: " ") ?? myStr.startIndex))) since it returns a Substring