在objectiveC中两个类的协议

主要问题是循环依赖，你可以把协议分离出来放到每天头文件里：
ClassA.h:

#import <Foundation/Foundation.h>
#import "ClassBProtocol.h"

@interface ClassA : NSObject <ClassBProtocol>
@end
ClassB.h:

#import <Foundation/Foundation.h>
#import "ClassAProtocol.h"

@interface ClassB : NSObject <ClassAProtocol>
@end
ClassAProtocol.h:

#import <Foundation/Foundation.h>

@protocol ClassAProtocol <NSObject>
...
@end
ClassBProtocol.h:

#import <Foundation/Foundation.h>

@protocol ClassBProtocol <NSObject>
...
@end

第二种方法这样：

ClassA.h:

#import <Foundation/Foundation.h>

@interface ClassA : NSObject
@end
ClassA.m:

#import "ClassA.h"
#import "ClassB.h"

@implementation ClassA () <ClassBProtocol>
@end

@implementation ClassA
@end
ClassB.h:

#import <Foundation/Foundation.h>

@interface ClassB : NSObject
@end
ClassB.m:

#import "ClassB.h"
#import "ClassA.h"

@implementation ClassB () <ClassAProtocol>
@end

@implementation ClassB
@end