I was asked by a co-worker why DBError is so bad… Here's my reply.

DBError

1) It's redundant. It adds _nothing_ to the class. You can do useful
things in an NSError subclass - you can localise the error description
automatically. But you don't want to expose your subclass to your
consumers unless there's a good reason for it. Dropbox could have used a
category and got what they were trying to achieve (although I believe
even that is redundant).

2) They change the type of NSError's code method from an NSInteger to
their own enum. There's no guarantee that when I compile with their
headers that the size of that enum _is_ the size of an NSInteger (e.g. I
compile my project with -fshort-enums and they don't…). I'm surprised
Xcode isn't bitching about this actually. Generally this doesn't matter,
I doubt even -fshort-enums would break it  But still - it's something
you shouldn't do as a general rule.

3) They force me to use DBErrors in my code as well as NSError and then:

NSError *error;
if ([… doSomething:&error] == NO)
    return;
if ([… doSomethingElse:&error] == NO)
	return;
if ([… doSomethingMore:&error] == NO)
	return;

Now it's:

NSError *error;
if ([… doSomething:&error] == NO)
	return;
DBError *dropboxError; // This error is SPECIAL
if ([… DBDoSomethingElse:&dropboxError] == NO)
	return;
if ([… doSomethingMore:&error] == NO)
	return;

So now I have an extra variable with a contrived name just because
someone at Dropbox decided to make a subclass. Thanks guys!

4: In simple methods I sometimes pass my method's error parameter to
methods I call so I don't even need an error variable. I can't  do that
with DBError:

- (BOOL)something:(NSError **)outError
	{
	// Do some work here…
	return [… dbDoSomethingElse:outError]; // Compile error?
	}

Imagine if they subclassed something else fundamental like NSURL or
NSString, added no functionality to it, and then expected me to use it
when interfacing with their APIs.

It's really redundant.

That combined with the DBError * vs ** parameters and I have to imagine
that this code was written by someone with little to no experience.

	Jon.

On Jul 10, 2013, at 6:07 XXXX wrote:

the pointer thing is just embarrassing i agree

Sent from my iPhone