iOS 主動拋出異常

Question:

What's the best way to throw an exception in objective-c/cocoa?

Answer:

Use [NSException raise:format:] as follows:

[NSException raise:@"Invalid foo value" format:@"foo of %d is invalid", foo];

此時控制台會Log：

*** Terminating app due to uncaught exception 'Invalid foo value', reason: 'foo of 9999 is invalid'*** First throw call stack:(0   CoreFoundation                      0x0083dca6 __exceptionPreprocess + 1821   libobjc.A.dylib                     0x004e18bf objc_exception_throw + 442   CoreFoundation                      0x0083dbcd +[NSException raise:format:] + 1413   Exception                           0x0000e9fb -[ViewController viewDidLoad] + 1394   UIKit                               0x00d3f2f4 -[UIViewController loadViewIfRequired] + 7715   UIKit                               0x00d3f5e5 -[UIViewController view] + 356   UIKit                               0x00c3a009 -[UIWindow addRootViewControllerViewIfPossible] + 667   UIKit                               0x00c3a47b -[UIWindow _setHidden:forced:] + 3148   UIKit                               0x00c3a6f8 -[UIWindow _orderFrontWithoutMakingKey] + 499   UIKit                               0x00c4931e -[UIWindow makeKeyAndVisible] + 8010  UIKit                               0x00be6e18 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 315911  UIKit                               0x00be9efb -[UIApplication _runWithMainScene:transitionContext:completion:] + 150712  UIKit                               0x00c02742 __84-[UIApplication _handleApplicationActivationWithScene:transitionContext:completion:]_block_invoke + 5913  UIKit                               0x00be8c3e -[UIApplication workspaceDidEndTransaction:] + 2914  FrontBoardServices                  0x030bcbce __37-[FBSWorkspace clientEndTransaction:]_block_invoke_2 + 4315  FrontBoardServices                  0x030bc834 __40-[FBSWorkspace _performDelegateCallOut:]_block_invoke + 5416  FrontBoardServices                  0x030ce455 __31-[FBSSerialQueue performAsync:]_block_invoke + 2617  CoreFoundation                      0x00762540 __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 1618  CoreFoundation                      0x007577d3 __CFRunLoopDoBlocks + 19519  CoreFoundation                      0x00756f38 __CFRunLoopRun + 93620  CoreFoundation                      0x007568cb CFRunLoopRunSpecific + 44321  CoreFoundation                      0x007566fb CFRunLoopRunInMode + 12322  UIKit                               0x00be8555 -[UIApplication _run] + 57123  UIKit                               0x00bebba5 UIApplicationMain + 152624  Exception                           0x0000eddd main + 14125  libdyld.dylib                       0x02af1ac9 start + 1)libc++abi.dylib: terminating with uncaught exception of type NSException

但實際上Apple並不建議我們拋出異常，耗費的資源太大。

Reference:

http://stackoverflow.com/questions/324284/throwing-an-exception-in-objective-c-cocoa