函数指针实现对象传递消息(回调)

//  AppDelegate.m

@implementation AppDelegate

int fun(int a, int b){

    return a + b;

}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    NSLog(@"%d",[a fucPointer:fun]);

    return YES;

}

//  A.h

#import <Foundation/Foundation.h>

@interface A : NSObject

- (int)fucPointer:(int (*)(int, int))fp;

@end

//  A.m

#import "A.h"

@implementation A

- (int)fucPointer:(int (*)(int, int))fp

{

    return fp(20,30);

}

@end