protocol类似@class方式使用, 能提高效率, 但是有警告.

main.m

#import "Dog.h"
#import "baseProtocol.h"
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
	@autoreleasepool {
		Dog * dog = [[Dog alloc] init];
		[dog run];
	}
	return 0;
}

baseProtocol.h

#import <Foundation/Foundation.h>

@protocol baseProtocol <NSObject>
- (void)run;
@end

Dog.h

#import <Foundation/Foundation.h>
@protocol baseProtocol;

@interface Dog : NSObject <baseProtocol> // 提示警告 :Cannot find protocol definition for 'baseProtocol' // 可以运行,但是有警告xcode7.0 不爽

@end

Dog.m

#import "Dog.h"
#import "baseProtocol.h"

@implementation Dog

- (void)run
{
	NSLog(@"dog is running");
}
@end