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

Answer 2

Something like this should work:

myMessage.substringToIndex(myMessage.characters.indexOf(" ")!)

Note that in this code I force unwrapped the optional. If you're not guaranteed to have that space in the string, it might make more sense to have the index in a optional binding.

With optional binding, it would look something like this:

if let index = myMessage.characters.indexOf(" ") {
    let result = myMessage.substringToIndex(index)
}

Answer 3

You can use a regex, try this code:

var myMessage  = "12345 is your number!"

if let match = myMessage.rangeOfString("-?\\d+", options: .RegularExpressionSearch) {

    print(myMessage.substringWithRange(match)) // 12345
    let myNumber = Int(myMessage.substringWithRange(match)) // Then you can initialize a new variable
}

The advantage is that this method extracts only the numbers wherever they are in the String

Hope this help ;)