对于ios开发者来说，反向传值再熟悉不过了。我们通常使用，代理，通知，block进行反向传值，今天我们通过demo一起看一下属性反向传值。例如A界面跳转到B界面。再从B界面往A界面传值。关键点在于B界面如何拿到跳过来的那个A界面。

AViewController.h

@interface AViewController : UIViewController

//声明一个公开的属性 用于接收 B界面回传的内容

@property(nonatomic)NSString *backVlaue;

@end

AViewController.m

//懒加载lable

-(UILabel *)label {

if(!_label) {

_label = [[UILabel alloc]initWithFrame:CGRectMake(100, 100, 200, 100)];

_label.font = [UIFont systemFontOfSize:24];

_label.backgroundColor = [UIColor yellowColor];

_label.text = @"初始内容";

[self.view addSubview:_label];

}

return _label;

}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

BViewController *bVC = [[BViewController alloc]init];

//将自己的地址给bVC中avc属性赋值 ，在bVC中通过avc这个属性，就可以找到当前对象

bVC.avc = self;

[self presentViewController:bVC animated:YES completion:nil];

}

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor = [UIColor whiteColor];

[self label];

}

-(void)viewWillAppear:(BOOL)animated {

[super viewWillAppear:animated];

if (!self.backVlaue) { return; }

//将传回的内容显示出来

self.label.text = self.backVlaue;

}

BViewController.h

@interface BViewController : UIViewController

//声明一个属性 用来保存前面 AVC实例的属性

@property(nonatomic)AViewController *avc;

@end

BViewController.m

-(UITextField *)field {

if (!_field) {

_field = [[UITextField alloc]initWithFrame:CGRectMake(100, 100, 200, 100)];

_field.backgroundColor = [UIColor yellowColor];

[self.view addSubview:_field];

}

return _field;

}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

//把输入的内容传回到前面界面

//获取文本框中的内容

//NSString *content = self.field.text;

//将内容创给 AVC (首先要找到AVC的实例)

self.avc.backVlaue = self.field.text;

[self dismissViewControllerAnimated:YES completion:nil];

}

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor = [UIColor greenColor];

[self field];

}

如图可以成功将B界面输入的字符串传送回来