Converting NSArray Contents to a varargs (With ARC) For Use With NSString initWithFormat

Question

We have some code today that takes an NSArray and passes it as a argument list to -[NSString initWithFormat:arguments] and we\'re trying to get this to work with ARC. Here\'s th

Answer 1

I tried mcfedr's code. Somehow, my Xcode 11 treated CVarArgType as undeclared type, so I investigated into this for a while.

I didn't not understand the closure part of his/her code. And, I just simplified to hard casted each element to CVarArg using as! operator.

func format(key: String, args: [Any]) -> String {
    return String(format: key, arguments: args.map { ($0 as! CVarArg) })
}

let doubleValue: Double = 1.25
let floatValue: Float = 2.75
let intValue: Int = 3
let numberValue: NSNumber = 4.5 as NSNumber
let hello: String = "Hello"
let world: NSString = "World" as NSString
print(format(key: "double: %f, float: %f, int: %d, number: %@, %@, %@", args: [doubleValue, floatValue, intValue, numberValue, hello, world]))

// double: 1.250000, float: 2.750000, int: 3, number: 4.5, Hello, World

It seems it's working fine under swift 5.1, but there may be some pitfalls.