a) The crash is from the default unhandled exception handler, which will send a signal to abort. So if you just want to crash, you can either handle that particular exception or install a different unhandled exception handler
b) An object gets sent the -forwardInvocation: message when objc_msgSend() encounters a message the object does not understand. The exception above gets raised by the default implementation of -forwardInvocation: in NSObject.
o := NSObject new.
o class
-> NSObject
n := NSInvocation invocationWithTarget:o andSelector: #class
n resultOfInvoking class
-> NSObject
o forwardInvocation:n
2019-04-22 07:49:12.339 stsh[5994:785157] exception sending message: -[NSObject class]: unrecognized selector sent to instance 0x7ff853d023c0 offset: {
(This shows that -forwardInvocation: in NSObject will raise that exception, even if the NSInvocation is for a message the object understands)
If you override -forwardInvocation:, you can handle the message yourself. In fact, that is the last-ditch effort by the runtime. You will first be given the chance to provide another object to send the message to ( - (id)forwardingTargetForSelector:(SEL)aSelector; ) or to resolve the message in some other way, for example by installing the method ( + (BOOL)resolveInstanceMethod:(SEL)sel; )[0].
Cocoa's undo system is implemented this way[1], as is Higher Order Messaging[2][3]
a) The crash is from the default unhandled exception handler, which will send a signal to abort. So if you just want to crash, you can either handle that particular exception or install a different unhandled exception handler
b) An object gets sent the -forwardInvocation: message when objc_msgSend() encounters a message the object does not understand. The exception above gets raised by the default implementation of -forwardInvocation: in NSObject.
(This shows that -forwardInvocation: in NSObject will raise that exception, even if the NSInvocation is for a message the object understands)If you override -forwardInvocation:, you can handle the message yourself. In fact, that is the last-ditch effort by the runtime. You will first be given the chance to provide another object to send the message to ( - (id)forwardingTargetForSelector:(SEL)aSelector; ) or to resolve the message in some other way, for example by installing the method ( + (BOOL)resolveInstanceMethod:(SEL)sel; )[0].
Cocoa's undo system is implemented this way[1], as is Higher Order Messaging[2][3]
[0] https://developer.apple.com/documentation/objectivec/nsobjec...
[1] https://developer.apple.com/documentation/foundation/nsundom...
[2] https://en.wikipedia.org/wiki/Higher_order_message
[3] https://github.com/mpw/HOM/blob/master/HOM.m