fake va_list in ARC

Question

I need to create in an iOS application a fake va_list to pass to a NSString initWithFormat:arguments: function, this is my code:

NS         


        

Answer 1

Its possible if you are willing to add a little bit of swift to your project!

The important bit is the mapping of NSArray to [CVarArgType] which is the swift equivalent for va_list. If you try to cast [AnyObject] to [CVarArgType] you cause run time crashes, but with the map we can explicitly make the needed list.

The rest of the code is the wrapper I made so that I can call this from obj-c. You could make a wrapper for any obj-c function that you want to call in this way.

@objc class StringFormat: NSObject {
    class func format(key: String, args: [AnyObject]) -> String {
        let locArgs: [CVarArgType] = args.map({ (arg: AnyObject) -> CVarArgType in
            if let iArg = (arg is NSNumber ? arg.intValue : nil) {
                return iArg
            }
            return arg as! CVarArgType
        });
        return String(format: key, arguments: locArgs)
    }
}