Re: Private Methods
Re: Private Methods
- Subject: Re: Private Methods
- From: Jonathan Hess <email@hidden>
- Date: Sat, 23 Feb 2008 14:15:28 -0800
On Feb 22, 2008, at 6:08 AM, Adam P Jenkins wrote:
On Feb 22, 2008, at 6:48 AM, Rob Petrovec wrote:
Lack of private methods is a serious flaw in Obj-C IMO.
This is silly. Private is really just about as voluntary in C++ as
it is in ObjC. If a user of your class wants to ignore your
decisions about what should be private methods, they have only to
write:
#define private public
#include "yourclass.h"
#undef private
void foo() {
YourClass obj;
obj.aPrivateMethod(); // no compiler errors or warnings
}
So declaring things private in C++ is just an advisory to users of
your class that certain methods and fields aren't intended to be
used by clients of the class, it's not meant as any kind of security
mechanism. In ObjC you can achieve the same thing by not declaring
methods in the interface file, so if a user of your class still
finds out about the method somehow and calls it, they'll get a
compiler warning and will know they're doing something not intended
by the class's author.
Note that this is in contrast to Java or C#, which run in managed
environments, and where private really can be used to fairly
securely block certain methods and fields from being accessed, when
using the correct security settings in the VM.
That said I do agree that it's nicer to have a formal language
construct for specifying what's private, like in C++, than the ad-
hoc mechanisms available in ObjC. I just don't agree that it's
really a serious flaw, more of a minor
flaw._______________________________________________
If a method is private, why would you ever want to place it in a
public header? I could see a justification for @proected applying to
methods, but it seems much better to just not have the private methods
in the interface at all. Putting a private method in the interface
says "This exists, and you can't use it." If I can't use it, why are
you telling me it is there?
I believe that in c++ the MyClass.h file is the *only* interface to
your class. In objective-c, the MyClass.h file is simply the public
interface to your class. You're free to have more than one @interface
and you are encouraged to use them to declare things that shouldn't be
part of your outward facing public interface.
Things would be best if we didn't even have to put our private
instance variables in the header -
Jon Hess
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