On 23 Aug 2013, at 4:49 AM, Kevin Meaney <k...@yvs.eu.com> wrote:
> I have a protocol where I would like to include the class method
> +(void)initialize as being required. This way all classes that conform to the
> protocol have to implement initialize as part of the protocol. I suppose I'm
> wondering if anyone perceives any problem with doing this?
>
> For example, will including +initialize as a required protocol method
> interfere with objective-c automatically calling the initialize method before
> the class is used for the first at runtime.
The threshold question is whether the compiler will enforce the protocol as you
wish. This is easy to test. The following code passes analysis and runs with no
problem:
-----
#import <Foundation/Foundation.h>
@protocol NeedsInitialize <NSObject>
+ (void) initialize;
- (void) mandatoryInstance: (NSString *) str;
@end
@interface NAImplementor : NSObject <NeedsInitialize>
- (NSInteger) anotherMethod;
@end
@implementation NAImplementor
- (void) mandatoryInstance:(NSString *)str
{
NSLog(@"%s gets string %@", __PRETTY_FUNCTION__, str);
}
- (NSInteger) anotherMethod
{
NSLog(@"%s sending -mandatoryInstance:", __PRETTY_FUNCTION__);
[self mandatoryInstance: @"NAImplementor sends mandatory"];
return 12;
}
@end
int main(int argc, const char * argv[])
{
@autoreleasepool {
NAImplementor * instance = [[NAImplementor alloc] init];
NSLog(@"%s implementor returns %li", __PRETTY_FUNCTION__,
(long)[instance anotherMethod]);
}
return 0;
}
-----
As I understand it, you want to require NAImplementor to have +[NAImplementor
initialize]. This code passes without this happening. It seems NSObject
implements +initialize, which is good enough to satisfy the protocol.
"Incomplete Objective-C Protocols," GCC_WARN_ALLOW_INCOMPLETE_PROTOCOL (Warn if
methods required by a protocol are not implemented in the class adopting it.
Only applies to Objective-C.), which is the closest warning I can find in short
order to what you want, is set YES, so if the warning worked as you hope, it
should have triggered.
You might have the +load method of the class introspect to see if it implements
+initialize, and throw an exception, but that requires a class hierarchy that
defeats the purpose of a protocol.
— F
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