On Apr 10, 2008, at 11:22 AM, Rama Krishna wrote:
I am new to Objective-C but I have done C++/C#/Java work. I have
been doing
some experiments to understand how the language works. I found that
it is
not necessary for an Objective-C class to derive from Object. I was
able to
create a class which did not derive from Object contrary to my
assumption
that all Objective-C classes implicitly derive from Object (such as
in C# or
Java).
However, such a class has a problem. It cannot be allocated or
initialized.
Because it can never get the alloc message as the alloc message is
declared
in the Object class. My question ,therefore, is how can such classes
be
instantiated. Is there a library function for that? Surely, the
standard
alloc function must be using such a function. Or should I just
derive all
classes from Object.
You need to implement said methods using lower level primitives
available on the system (malloc(), for example)! And you'll likely
need to implement a boatload of other methods, depending on what level
of interoperability you want with the rest of Cocoa.
However, as someone else indicated...
... you probably do not want to create your own base class. If you
look at Cocoa, you'll find that there are very very few base
classes. NSProxy is about the most prominent one. Unless you
really do need to create a new class hierarchy with very different
semantics than the hierarchy derives from NSObject, there is no reason
to do define a new root class.
NSObject (Not "Object", btw, as-- in the context of Cocoa-- that
refers to pre-1992 APIs) presents a tremendous amount of functionality
that provides the foundation on top of which much of Cocoa is
implemented; KVO, KVC, bindings, allocation, reference counting, GC,
etc.
b.bum
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