Re: Programming it's a play

[Dennis Leeuw]

As I am still learning programming the following part is not something I 
knew. I had wondered what the - sign was for, but had not figured it out 
yet.

> Two types of methods exists as you know : class methods (+) and instances
> methods (-). Class methods only works on the class itself, instances 
> methods
> only works on an instance of a class (ie, an object). imho speaking of 
> "class objects"
> is a bit misleading -- as the definition of an object is to be an 
> instance of a class...
> you could send messages directly to the class, but it's not an object 
> per se...


I do want to know what this means. Can someone that writes a class, like 
the Greeter example write his own Class methods or are Class methods 
just inherited from the root class. Meaning you can only add instance 
methods.

What is your view on a class (remember I am a VERY newbie). How can you 
send a message to a class when a class is not an object.

From the Apple documentation: 
http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/3objc_language_overview/index.html
I got:
The compiler creates just one accessible object for each class, a class 
object that knows how to build new objects belonging to the class. (For 
this reason it's traditionally called a "factory object.") The class 
object is the compiled version of the class; the objects it builds are 
instances of the class. The objects that will do the main work of your 
program are instances created by the class object at runtime.

And:
To get an object to do something, you send it a message telling it to 
apply a method.
...
The receiver is an object, and the message tells it what to do.

This to me means that messages can only be send to objects. That a class 
is the written definition of an object. And that the compiled version is 
a class object.

The last two sentences are important imho. Since a class is a written 
definition it can NOT be send a message. You can only send messages to 
class objects (the compiled version).

Help, help, help it gets more and more confusing.

Dennis