iosswift4variadic

Passing variadic args in Swift 4 for os_log

I am trying to write a convenience wrapper for os_log in Swift 4 / iOS 11, but I've run into an uphill battle with passing the variadic arguments.

Basically, I want to write a function that looks like the following.

static let logger = OSLog(subsystem: "com.example.foo", category: "foobar")
func logError(_ message: StaticString, _ args: Any...) {
    os_log(message, log: logger, type: .error, args)
}

Unfortunately, I can't seem to figure out the magic syntax to get the arguments passed along and have gotten a bit lost in the quagmire of CVarArg discussions.

(... this makes me miss Python's splatting syntax)

Solution

  • Did some more research on this. Turns out that os_log is actually a C macro. This created all sorts of problems with how it maps in to Swifts variadic args.

    However, that macro also captures other debugging info and is probably not safe to wrap up anyways.