On 3 Oct 2009, at 20:20, Colin Howarth wrote:
OK, skipping the melodrama, there's something wrong with the Apple
documentation,
but I can't quite put my finger on it.
The Perl man pages on nested data structures, say a dictionary
containing arrays containing
other dictionaries which are actually representing objects, I find
perfectly clear, for example.
And I did the first time I read it.
Take the Key-Value Coding Programming Guide which describes the
NSKeyValueCoding informal protocol which
defines a mechanism allowing applications to access the properties
of an object indirectly
by name (or key), rather than directly through invocation of an
accessor method or as instance variables.
Translation: You'll find lots of useful things can happen if you
access your instance variables
(e.g. the variable bar of the instance foo) like this: baz =
foo.bar; foo.bar = baz; which is just
shorthand for baz = [foo bar]; and [foo setBar: baz]; . Other parts
of your code can access bar simply
by knowing the string @"bar".
Actually, that's not a translation, it's more or less (less rather
than more, I admit) the entire Key-Value
Coding Programming Guide. At least, it's enough to get you going.
Well for a start your translation is wrong. Being able to do this:
baz = foo.bar;
foo.bar = baz;
is an Objective-C 2.0 feature – Dot Notation. It is completely
orthogonal to Key-Value Coding.
Dot Notation works by the compiler figuring out which method calls the
dots correspond to.
Key-Value Coding happens at run-time where the object receives a -
valueForKey: or -setValue:forKey: message and then decides how to
handle it based upon the key.
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