代理回调传值

在需要传值的视图接口 声明一个代理 delegate

PushViewController.h中代码

@protocol PushViewControllerDelegate ;
@interface PushViewController : UIViewController
@property (weak, nonatomic) IBOutlet UITextView *pushTextView;
@property (nonatomic,weak) id <PushViewControllerDelegate>delegate;
@end
@protocol PushViewControllerDelegate
-(NSString *)sendValue:(NSString *)message;
@end
//:为什么不写在接口上面呢？ 这样会暴露 内部方法;所以要在上面声明一下这个协议

PushViewController.m代码

- (void)viewDidLoad {
[super viewDidLoad];
 _pushTextView.text = [_delegate sendValue:nil];
  // Do any additional setup after loading the view.
}
//:视图消失的时候将值传过去
-(void)viewWillDisappear:(BOOL)animated {
   [super viewWillDisappear:animated];
_pushTextView.text =  [_delegate sendValue:_pushTextView.text];
}

ViewController.h中要实现该代理

ViewController.m文件中

-(NSString *)sendValue:(NSString *)message {

    _textView.text = message;

    return _textView.text;

}
 再prepareForSegue 跟PushViewController进行连线，表明是从PushViewController那边取值
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    PushViewController *pushViewController  =  segue.destinationViewController;

    pushViewController.delegate = self;

}