On 12 Jun 2008, at 13:01, Graham Cox wrote:
On 12 Jun 2008, at 5:47 pm, Chris Suter wrote:
Can you give me a counter-example?
Let’s say the function your calling uses one of the following:
-[NSDictionary setObject:forKey:]
-[NSMutableArray addObject:]
Raising an exception is a good response when a nil argument isn't
appropriate, but that only shows those methods are correctly dealing
with that anticipated situation. Plenty of other code uses nil to
mean "use the default", or is harmless.
Sort of, yes. I think Chris's point was that you can't assume that
you can pass nil arguments to any method and expect that they will
just cause some sort of no-op. In the cases he lists that's clearly
not what happens.
+[NSDictionary dictionaryWithObjectsAndKeys:Object1, Key1,
ObjectThatIsNil, Key2, Object3, Key3, nil]
Actually that effect can be extremely handy. For example the
userInfo dict to a notification can often be set up in order such
that optional info can be nil - that terminates the list early and
perfectly safely
I'm not sure it's a great idea to rely on this, since I think it falls
into the realm of Behaviour That Is Not Obvious. But I can see it
might be useful in some circumstances. Again, however, passing nil
didn't have a no-op result; it did something quite different and which
(if ObjectThatIsNil is a parameter to some other method) might be
highly counter-intuitive.
Kind regards,
Alastair.
--
http://alastairs-place.net
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