On Jan 23, 2009, at 3:01 PM, Horst Jäger wrote:
suppose I have a class with a private member as listed at the end of
this email.
Then I can access it by calling its name without an accessor
function (which would de facto make it public).
But how do I access a private member of another object of the same
class?
@interface PrivateClass : NSObject {
@private int mineAlone;
}
-(int)yoursToo;
-(int)yoursTooButWithAnother: (PrivateClass *)another;
@end
@implementation PrivateClass
-(int)yoursToo{
// access via name works
return mineAlone % 3;
// I cant't use
// return [self mineAlone]
// using a getter function
// because that would make
// mineAlone accessible for
// everyone since a method
// can't be declared private
There's no real way to enforce privateness, either in Objective-C or C+
+. Generally, you have to trust the code which uses your class to
some extent. The typical approach is to merely make sure that the
other code gets a warning from the compiler if they do something they
shouldn't.
In Objective-C, this is accomplished by not declaring the method in
the header. In the implementation, you can define it above where you
use it. Or, you can use Objective-C 2.0 class extensions to declare
it. Or, prior to Objective-C 2.0, you can define a category in
your .m file to declare it.
}
-(int)yoursTooButWithAnother: (PrivateClass *)another;
// what am I to do?
// return another.mineAlone % 3;
// won't work and
But another->mineAlone will.
// return [another mineAlone] % 3;
// would de facto make it public
See above.
}
@end
Cheers,
Ken
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