CODEWITHSUNDEEP
iosobjective-cnsstringnsexceptioncrittercism
Sinu Varghese
Sinu Varghese

Reputation: 800

Objective-C : appending a NSString to NSException reason

I am working on some API (Crittercism) to report handled exceptions in the client to server.

The client API takesNSException as the input parameter. I have to add some application context info string(NSString) also to theNSException before calling the API.

How I can do it using Objective-C.

NSString* appContextString;


NSString *test = @"test";
unichar a;
int index = 5;

@try {
    a = [test characterAtIndex:index];
}
@catch (NSException *exception) {
    // add app context to exception before reporting to Crittercism.
    [Crittercism logHandledException:exception]; 
}

I have to append appContextString to exception.

Upvotes: 1

Views: 1372

Answers (2)

Amin Negm-Awad
Amin Negm-Awad

Reputation: 16660

You have to copy it. This can be done easily. An instance of NSExeption has three important properties:

  • name
  • reason
  • user info

When copying it, you can add a string to the user info dictionary:

NSMutableDictionary *userInfo = [exception.userInfo mutableCopy];
userInfo[@"YourPrivateKey"] = contextString;
NSException *extendedException = [NSException exceptionWithName:exception.name reason:exception.reason userInfo:userInfo];

I think as a caveat that you will lose the call stack. You can read that and put it in the user info dictionary, too. I do it a similar way on Objective-Cloud.

userInfo[@"CallStackSymbols2] = exception.callStackSymbols;

Analogous with call stack return addresses.

I do not think that this is very nice, because the call stack becomes a part of the exceptions's user info instead of the exception itself. For me this is no caveat, because I sent the exception as JSON, therefore the call stack as JSON object. I cannot say, whether this is a problem for you.

Upvotes: 1

trojanfoe
trojanfoe

Reputation: 122391

You could build a new NSException object from attributes of the old one, but that seems very messy. As you are just logging the handled exception, I would simply log the "app context" before that:

@try {
    a = [test characterAtIndex:index];
}
@catch (NSException *exception) {
    NSString *appContext = @"...";
    [Crittercism leaveBreadcrumb:appContext];
    [Crittercism logHandledException:exception]; 
}

Upvotes: 1

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