Re: Confusing problems with inheritance in Objective-C
Re: Confusing problems with inheritance in Objective-C
- Subject: Re: Confusing problems with inheritance in Objective-C
- From: Darren Ford <email@hidden>
- Date: Tue, 22 Jun 2004 16:03:31 +1000
On 22/06/2004, at 2:12 PM, Chris Hanson wrote:
On Jun 21, 2004, at 7:31 PM, Darren Ford wrote:
I've been programming in C++ for many years now, and I think the
problem is probably that I haven't fully understood the Obj-C concept
of inheritance and I'm trying to use my C++ knowledge to define my
class. Can anyone shed any light on why I'm seeing this problem?
I've attached my class definitions to the end of the email.
Another more general style critique on your code: You're creating a
subclass of NSMutableDictionary, but it looks like you're doing so
just to use a mutable dictionary rather than in order to create a new
kind of mutable dictionary.
In such a case, it's generally better to just have a mutable
dictionary that's referenced by an instance variable. That way you
just have a has-a relationship rather than an is-a relationship.
I agree -- actually the reason for doing this way is that I want to use
Cocoa's built-in property serialization class to be able to write an
array of these 'objects' out to a file. Creating a new class and then
creating a 'has-a' relationship with NSMutableDictionary won't work in
my situation, as the NSPropertyListSerialization class is limited to
NSData, NSString, NSArray, NSDictionary, NSDate, and NSNumber objects.
By creating an is-a relationship with NSMutableDictionary I was hoping
to leverage this, rather than having to write my own encoding methods.
Darren.
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