Swift String附加可选的nil

Question

The second way of printing an optional value is correct, but is there any shorter way to write code with the same effect? Ie Where before unwrapping the value we check if its nil.

var city:String?

func printCityName(){
    let name = "NY"
    //Fails (First Way)
    print("Name of the city is \(name + city)")
    //Success (Second Way)
    if let cityCheckConstant = city {
       print("Name of the city is \(name + cityCheckConstant)")
    }
}

Answer 1

Shortest would be with map on the Optional:

var city : String?

func printCityName() {
    let name = "NY"
    city.map{ print("Name of the city is \(name + $0)") }
}

Or guards are nice too:

func printCityName(){
    let name = "NY"
    guard let city = city else { return }
    print("Name of the city is \(name + city)")
}

Your code was alright though, a more readable version is always better when it does the same. One thing to mention: You don't have to use a different name for the variable in the if let :

func printCityName(){
    let name = "NY"
    if let city = city {
        print("Name of the city is \(name + city)")
    }
}

EDIT:

If you don't like to use _ = every time with the first version, you can extend Optional :

extension Optional {
    func with(@noescape f: Wrapped throws -> Void) rethrows {
        _ = try map(f)
    }
}

which makes it possible to do this:

func printCityName() {
    let name = "NY"
    city.with{ print("Name of the city is \(name + $0)") }
}

without a warning