@throws or NSError which one is appropriate in for objective C api kind of methods

Question

Which one is the most preferred objective C exception handling ? NSError pointer which give the pointer with message details within it or @throws which forces the caller to handle exception and show some graceful message. Thanks.

and alos please let me know which one is memory efficient.

You are confusing exception handling with error handling. There's a reason Apple made two different classes - `NSException` and `NSError`. — , Jul 09 '13 at 21:38
In short, don't throw an exception unless some internal inconsistency, assertion failure, etc. happens. If the web API returned an error, the user entered an invalid password or your mother-in-law has stomach ache, report it back to the caller function using an `NSError`. — , Jul 09 '13 at 21:40

score 3 · Accepted Answer · answered Jul 09 '13 at 21:48

Unlike Java, in Objective-C exceptions are just used to handle unrecoverable states. This means that for example, you don't catch EXC_BAD_ACCESS, rather you debug your application and correct the problem.

The Objective-C equivalent of Java exceptions is NEError and the null pointer pattern. For example if a formatter fails to format a string to a number because the string does not represent a number, it returns nil. There is also a method to format the number that takes a NSError double pointer to return the error description.

So to handle errors you typically implement a method like this:

- (id) object : (out NSError**) error
{
    BOOL ok= ... 
    if(!ok)
    {
        if(error)
            *error= ...
        return nil;
    }
    return someObject;
}

@throws or NSError which one is appropriate in for objective C api kind of methods

1 Answers1