Property semantics - private vs public APIs

Question

Hi,
Question about property directives and how to enable separate public and private semantics.
In my class's public interface I would like a property to be read only so I declare it as follows:
@property (readonly) someproperty;
However, within the class I would like to set the property and have the convenience of retain being called and set to nil through the property so the release happens. So I would do the following:
@property (retain) someproperty;
Now the two semantics are not entirely mutually exclusive. I could do the following:
@property (readonly , retain) someproperty;
However, external users of the class can use the setter which is not what is intended. Coming from a Java and C# background it seems that objecive-c does not provide as robust a syntax for making clean distinctions between public and private interfaces.
What strategies can you suggest to achieve my goals of keeping my private and public semantics and usage clear? Any good web resources on the broader subject of best practices in API design in objective-c?

Answer 1

Yes class-dump can always be used to generate public interfaces in a hostile world but that's not really the point. The issue is how to generate clean interfaces for a team of software developers. Anyway after talking to Matt, I have answered my own question: a synthetic property, a category plus a hand coded setter will make this work. Once the bug in @synthesize is fixed this will be nice solution to the problem.
Here are a few bits to illustrate:
In MyClass.h
@interface MyClass
@property (readonly) id someProperty;
@end
In MyClass.m
#import "MyClass.h"
@interface MyClass (Private)
@property (retain) id someProperty;
@end
@implementation MyClass
@synthesize someProperty;
// Bug - hand written setter needed since @synthesize will not generate one for me
- (void) setSomeProperty: (id)newProperty
if (newProperty != someProperty)
[someProperty release];
someProperty = [newProperty retain];
@end
Files that import MyClass.h will only have access to the getter while the setter is available to MyClass.m.