Objective-C : appending a NSString to NSException reason

Question

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.

Can you show what you have tried and any errors you're currently getting? — App Dev Guy, May 19 '15 at 07:00

score 1 · Answer 1 · answered May 19 '15 at 07:10

1

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]; 
}

answered May 19 '15 at 07:10

trojanfoe

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I would prefer to build a new NSException object from the attributes of the old one. – Sinu Varghese May 19 '15 at 07:25
@SinuVarghese So, why don't you do it? – Amin Negm-Awad May 19 '15 at 07:36
@AminNegm-Awad, I have only less knowledge in Objective-C, So I don't know how to do it. – Sinu Varghese May 19 '15 at 07:42
Does the Crittercism console show the complete `NSException` details? If so following @AminNegm-Awad's (now deleted) answer would be best as you can put the "app context" within the exception's `userInfo` dictionary, rather then messing with the exception string. – trojanfoe May 19 '15 at 07:47
@trojanfoe- Yes,Crittercism console shows the complete NSException details. I couldn't see Amin Negm-Awad's answer. Could you please post that code. – Sinu Varghese May 19 '15 at 07:58
@AminNegm-Awad Please undelete your answer. – trojanfoe May 19 '15 at 08:01
@trojanfoe userInfo is a eadonly property – Amin Negm-Awad May 19 '15 at 09:01
@AminNegm-Awad Ah. So you need to build a new exception from scratch. Sounds really tedious. – trojanfoe May 19 '15 at 09:04
@trojanfoe Yeah, and I do not really understand what makes the *user*Info dictionary read only. – Amin Negm-Awad May 19 '15 at 09:10

Amin Negm-Awad · Answer 2 · 2015-05-19T09:34:04.243

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.

Objective-C : appending a NSString to NSException reason

2 Answers2