Swift function with args… pass to another function with args

Question

I have a simple problem. I tried search in many blogs about this question but all site return how function in swift work, but I need this case.

My custom function is

Answer 1

I believe you're using NSString.localizedStringWithFormat(self, args) incorrectly. Otherwise nothing wrong with using args to call another function.

If you look below, you need to specify the format as NSString as the first argument: NSString.localizedStringWithFormat(format: NSString, args: CVarArgType...)

This SO question explains how to use it in Swift: iOS Swift and localizedStringWithFormat

Answer 2

Similar as in (Objective-)C, you cannot pass a variable argument list directly to another function. You have to create a CVaListPointer (the Swift equivalent of va_list in C) and call a function which takes a CVaListPointer parameter.

So this could be what you are looking for:

extension String {
    func getLocalizeWithParams(args : CVarArgType...) -> String {
        return withVaList(args) {
            NSString(format: self, locale: NSLocale.currentLocale(), arguments: $0)
        } as String
    }
}

withVaList() creates a CVaListPointer from the given argument list and calls the closure with this pointer as argument.

Example (from the NSString documentation):

let msg = "%@:  %f\n".getLocalizeWithParams("Cost", 1234.56)
print(msg)

Output for US locale:

Cost:  1,234.560000

Output for German locale:

Cost:  1.234,560000

---

Update: As of Swift 3/4/5 one can pass the arguments to

String(format: String, locale: Locale?, arguments: [CVarArg])

directly:

extension String {
    func getLocalizeWithParams(_ args : CVarArg...) -> String {
        return String(format: self, locale: .current, arguments: args)
    }
}