ios - How should I use NSSetUncaughtExceptionHandler in Swift

Question

At Objective-C, I call the NSSetUncaughtExceptionHandler(&exceptionHandler) method to log exceptions. How does it called in Swift?

Answer 1

As of Swift 2 (Xcode 7), you can pass Swift functions/closures to parameters taking a C function pointer. From the Xcode 7 release notes:

Native support for C function pointers: C functions that take function pointer arguments can be called using closures or global functions, with the restriction that the closure must not capture any of its local context.

So this compiles and works:

func exceptionHandler(exception : NSException) {
    print(exception)
    print(exception.callStackSymbols)
}

NSSetUncaughtExceptionHandler(exceptionHandler)

Or with an "inline" closure:

NSSetUncaughtExceptionHandler { exception in
    print(exception)
    print(exception.callStackSymbols)
}

This does exactly the same as the corresponding Objective-C code: it catches otherwise uncaught NSExceptions. So this will be caught:

let array = NSArray()
let elem = array.objectAtIndex(99)

NOTE:- It does not catch any Swift 2 errors (from throw) or Swift runtime errors, so this is not caught:

let arr = [1, 2, 3]
let elem = arr[4]