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iOS Closures in Swift 2 First Class Functions Higher Order Functions

nicholasdevereaux
nicholasdevereaux
16,353 Points
Posted by nicholasdevereaux
nicholasdevereaux
16,353 Points

Closures - how to use 'characters' property without force unwrapping?

In this task, we are asked to use the 'characters' property to return the first letter in the string passed through the function. The only way I could get it to work was by using the "!"

I also found a way to make it work by using 'index'. Which function would make more sense here?

functions.swift 
// Enter your code below
extension String {
    func modify(aString: String -> String) -> String {
        return aString(self)
    }
}

func firstLetter(b: String) -> String {
    return "\(b[b.startIndex])"
}

func firstLetter(a: String) -> String {
    return String(a.characters.first!)
}

1 Answer

jcorum
jcorum
71,830 Points

nicholas, as you say, they ask you to use characters, so here's an alternative. Doesn't seem any better than yours, however:

func firstLetter(b: String) -> String {
    return "\(b[b.characters.prefix(0)] )"
}

You can also get the first character and then cast it to a String (without the forced unwrapping):

func firstLetter(b: String) -> String {
    return "\(String(b.characters.first))"
}
nicholasdevereaux
nicholasdevereaux
16,353 Points
nicholasdevereaux
nicholasdevereaux
16,353 Points

Jcorum thanks for sharing, this really helped!