Re: ObjectiveC accessors

[Stefan Urbanek]

On 2004-05-30 12:04:19 +0200 David Ayers <address@hidden> wrote:

> Stefan Urbanek wrote:

<snip>

> > I was thinking about some decent inclusion of accessors in the ObjectiveC 
> > while maintaining language simplicity. After many attempts, through various 
> > @accessor and @getter I came with following simple and extensible language 
> > syntax:
> >
> > @interface MyClass:NSObject
> > {
> >       NSString *name : public retained;
> >       NSArray  *collection : public readonly;
> >       NSString *weakReference : public nonretained;
> > }
> > - someInstanceMethod;
> > @end
> >
> > So the syntax is:
> > @interface ...
> > {
> >       <ivar> : <keyword list>
> > }
> >
> > where keyword list is space separated list of ivar attributes. The keywords 
> > used are just examples, feel free to imagine others that can be more 
> > appropriate. Meaning of the above keywords is:
> > "public" - automaticaly generate getter and setter methods for the ivar 
> > -[MyClass ivarName] and -[MyClass setIvarName:]
> > "retained" - use [ivar retain] in the setter method
> > "nonretained" - do not use [ivar retain] in the setter method (one of the 
> > two retained and nonretained should be default)
> > "readonly" - do not generate the setter method
<snip>

> Well actually the "retain/release/autorelease" paradigm is outside of the 
> scope of the ObjC language.  It's a part of the OpenStep specification and 
> it's derivatives.  There are however various macro based approaches to this 
> issue.  Maybe a semi "standardized" set of such macros could be a future 
> feature of OpenStep derivatives.

Currently I am using:

#define GETTER(type, attr, capattr) \
    - (type)attr { return attr; }

#define SETTER(type, attr, capattr) \
    - (void)set##capattr:(type)value { attr = value; }

#define ACCESSORS(type, attr, capattr) \
    GETTER(type, attr, capattr) \
    SETTER(type, attr, capattr) \

#define RGETTER(type, attr, capattr) \
    - (type)attr { return attr; }

#define RSETTER(type, attr, capattr) \
    - (void)set##capattr:(type)value { ASSIGN(attr,value); }

#define RACCESSORS(type, attr, capattr) \
    RGETTER(type, attr, capattr) \
    RSETTER(type, attr, capattr)

and apply it as:

    RACCESSORS(NSString *, rootObjectNames, RootObjectNames)
    RACCESSORS(NSArray *, prototypes, Prototypes);
    RACCESSORS(NSDictionary *, objects, Objects);

However, I still need to write @interface method entries for both, getter and 
setter, so I have to write it in: ivar list, @interface method list, and 
@implementaion. And this is what I would like to avoid: to write single pattern 
on three places.

Speaking about retain/release being OpenStep specific. Why not to include some 
kind of garbage collection into the language too? It is used in majority of 
sources. Of course, with appropriate library hooks/callbacks, so one can 
implement custom GC method. I think it can be done in some simple way.

Stefan
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