Noobie Questions

Hi everybody. First off, I'd like to say I'm a complete noobie at
Objective C/Cocoa programming, but I'm trying really hard to get
things down. I'm really trying to learn how to program for the iPhone.
I have some questions that are probably extrememly basic, but I
haven't found any real answers for online or in any Objective-C/Cocoa
book (I'm sure the answers are out there, I just can't find it).

1. What is the difference between brackets and parenthesis?

For example, what is the difference between these

[NSString someMethod]

and

(NSString *) someMethod

2. Is there a way to determine object type in an array (or just in
general)?

For example, lets say I had a simple inheritance setup: abstract car
class with subclasses for Honda, Ford, Toyota, Dodge, etc. Now I
create a mutable array of car objects and fill it with various
subclass objects. Is there a function to determine the object type of
a specific element in the array?

3. I am really lost when it comes to creating constants and
enumerations

Lets say I have the following code:

const screenWidth = 320;
const screenHeight = 480;
enum week { Mon, Tues, Wed, Thurs, Fri, Sat, Sun };

Where do I place this code? Does it belong in a header file in the
@interface section or in the @implentation section, or some other
obscure place? I've seen quite a few different opinions online, but
I'd like to learn the correct way to do this.

I apologize if these questions are "too noobish" but I am a beginner.
Also if anyone has any books or websites they'd recommend, I'm all
ears. Thanks in advance.

In article
<75d8031e-7183-47c5-937d-e918b435aa54 RemoveThis @z23g2000prd.googlegroups.com>,
SLR <Sean.Raborg RemoveThis @gmail.com> wrote:

> Hi everybody. First off, I'd like to say I'm a complete noobie at
> Objective C/Cocoa programming, but I'm trying really hard to get
> things down. I'm really trying to learn how to program for the iPhone.
> I have some questions that are probably extrememly basic, but I
> haven't found any real answers for online or in any Objective-C/Cocoa
> book (I'm sure the answers are out there, I just can't find it).
>
> 1. What is the difference between brackets and parenthesis?
>
> For example, what is the difference between these
>
> [NSString someMethod]

This attempts to call a class method named someMethod on the NSString
class (not on any particular NSString instance). You'd need to add a
semicolon to make it complete. Even then it would only compile if
"someMethod" is actually a placeholder you're using for a method that
actually exists on NSString.
>
> and
>
> (NSString *) someMethod

This is (almost) a declaration of a method that takes no arguments and
returns an NSString. To be complete it needs either a "+" or "-" at the
start to indicate whether it's a class method or an instance method.

> 2. Is there a way to determine object type in an array (or just in
> general)?
>
> For example, lets say I had a simple inheritance setup: abstract car
> class with subclasses for Honda, Ford, Toyota, Dodge, etc. Now I
> create a mutable array of car objects and fill it with various
> subclass objects. Is there a function to determine the object type of
> a specific element in the array?

You can call the "class" method on any object to get a reference to its
class object. You can use "isKindOfClass" to ask an object if it's an
instance of a specific class.

> 3. I am really lost when it comes to creating constants and
> enumerations
>
> Lets say I have the following code:
>
> const screenWidth = 320;
> const screenHeight = 480;
> enum week { Mon, Tues, Wed, Thurs, Fri, Sat, Sun };
>
> Where do I place this code? Does it belong in a header file in the
> @interface section or in the @implentation section, or some other
> obscure place? I've seen quite a few different opinions online, but
> I'd like to learn the correct way to do this.

There's no single right answer, it depends on where you want those
declarations to be available. C scoping rules offer a variety of
solutions depending on what you need to have happen.

--
Tom "Tom" Harrington
Independent Mac OS X developer since 2002
http://www.atomicbird.com/