ios - throwing custom exception in objective c -

i have following code . . .

@try {     nsarray * array = [[nsarray alloc] initwithobjects:@"1",@"2",nil];     // below code raise exception     [array objectatindex:11]; } @catch(nsexception *exception) {     // want create custom exception , throw .      nsexception * myexception = [[nsexception alloc] initwithname:exception.name                                                            reason:exception.reason                                                          userinfo:exception.userinfo];      //now saving callstacksymbols mutable array , adding objects      nsmutablearray * mutablearray = [[nsmutablearray alloc]                                         initwitharray:exception.callstacksymbols];      [mutablearray addobject:@"object"];      //but problem when try assign mutable array myexception getting following error      myexception.callstacksymbols = (nsarray *)mutablearray;      //error : no setter method 'setcallstacksymbols' assignment property      @throw myexception;  } 

please fix , wanted add objects callstacksymbols . . . .thanks in advance

if coming java background, exception handling in objective-c feels strange @ first. in fact don't use nsexception own error handling. use nserror instead, can find @ many other points through sdk, when handling unexpected error situations (e.g. url operations).

error handling done (roughly) this:

write method takes pointer nserror parameter...

- (void)dosomethingthatmaycauseanerror:(nserror*__autoreleasing *)anerror {     // ...     // failure situation     nsdictionary tuserinfo = @{@"mycustomobject":@"customerrorinfo"};     nserror* terror = [[nserror alloc] initwithdomain:@"mydomain" code:123 userinfo:tuserinfo];     anerror = terror; } 

the userinfo dictionary place put whatever information needs provided error.

when calling method, check error situation this...

// ... nserror* terror = nil; [self dosomethingthatmaycauseanerror:&terror]; if (terror) {     // error occurred!     nsstring* tcustomerrorobject = [terror.userinfo valueforkey:@"mycustomobject"];     // ... } 

if calling sdk method result in "nserror != nil", can add own information userinfo dictionary , pass error caller shown above.