RE: id versus Class
RE: id versus Class
- Subject: RE: id versus Class
- From: "Mondragon, Ian" <email@hidden>
- Date: Wed, 05 Mar 2003 15:03:44 -0600
yes and no :-)
you are correct about the id - it's a generic pointer to an instance whose
class is not known until runtime. but the Class is a pointer to a *class*
structure (not an instance of it) whose identity is not known until runtime
- think of it as an id for classes themselves, rather than instances:
Class unknownClass = Nil; // capital "N" for classes
id unknownInstance = nil; // lower-case "n" for instances
// act like you really want a new instance of a pre-existing object
called "someRandomObject"...
unknownClass = [someRandomObject class];
unknownInstance = [[unknownClass alloc] init];
// now do whatever you will...
- ian
>
-----Original Message-----
>
From: Britt Green [SMTP:email@hidden]
>
Sent: Wednesday, March 05, 2003 2:43 PM
>
To: email@hidden
>
Subject: id versus Class
>
>
> Message: 15
>
> Date: Wed, 05 Mar 2003 13:08:57 -0600
>
> From: "Mondragon, Ian" <email@hidden>
>
> Subject: RE: Newbie coming to Cocoa from the world of C++
>
> To: email@hidden, email@hidden
>
>
<in deletia>
>
>
> 4) an id is an un-typed pointer to an object instance (determined at
>
> runtime). a Class is a pointer to a class data structure:
>
>
>
> id foo = [[AnyClass alloc] init];
>
> id bar
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> Class baz = [AnotherClass class];
>
>
>
> bar = [[baz alloc] init];
>
>
So id is used when the class may not be known, and Class is used when
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the object *is* known, correct?
>
>
> hope that helps a bit...
>
>
It does. Thank you, and to everyone else who wrote me, answering my
>
questions.
>
>
Best,
>
>
Britt
>
>
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>
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