Question

I want to try to create an image using NSdata. If imageWithData: method of UIImage can create it successfully, i will follow a path but if it cannot create i want to follow another way.

Is this even possible?

I tried

    @try {
        im = [UIImage imageWithData:data];
        NSLog(@"Trying");
    }
    @catch (NSException * e) {
        NSLog(@"Exception");    
        anotherData = doSomethingWithData(data)
        im = [UIImage imageWithData:anotherData];
    }
    @finally {
        NSLog(@"Final");
        [self.questionList addObject:im];
    }

but it causes app to crash.

How can I catch this exception without causing app to crash?

Exception is this:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSMutableArray insertObject:atIndex:]: attempt to insert nil object at 0'

Code does not create image from data but still it does not throws an exception or anything about it. Is there a way that I can understand if image is created or not.

Answer 1

You get the error, because im remains nil and you are not allowed to add nil to an array.

You could do it like that:

im = [UIImage imageWithData:data];

if(im == nil) {
    anotherData = doSomethingWithData(data)
    im = [UIImage imageWithData:anotherData];
}

if(im != nil)
    [self.questionList addObject:im];