一般来说有以下几种方式进行传值：

1.委托代理(delegate)

2.通知notification方式

3.Block方式

4.UserDefault或者文件形式

5.单例模式方式

6.属性传值

下面分情形对几种传值方式进行说明：

(1).从A页面跳转到B页面

方法：在B页面控制器中设置一个属性，在A页面跳转至B页面的时候，将B的属性赋值即可

@property(nonatomic) NSInteger flag;

- (IBAction)showSecondView:(id)sender {
    SecondViewController *second = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
    second.delegate = self;
    second.flag = 0;
    [self presentViewController:second animated:YES completion:nil];
}

(2).A页面跳转到B页面，B页面再跳转到A页面

解决办法1：使用delegate进行传值。例子如下：

设置协议和方法:

//SecondViewController.h
@protocol secondViewDelegate
-(void)showName:(NSString *)nameString;
@end

@interface SecondViewController : UIViewController
@property (nonatomic, weak)id<secondViewDelegate> delegate;
@property (nonatomic, copy) ablock block;
@end

//SecondViewController.m
- (IBAction)delegateMethod:(id)sender {
    if ([self notEmpty]) {
        [self.delegate showName:self.nameTextField.text];
        [self dismissViewControllerAnimated:YES completion:nil];
    }else{
        [self showAlert];
    }
}

//RootViewController.m
-(void)showName:(NSString *)nameString{
    self.nameLabel.text = nameString;
}

记得要设置delegate的指向！

解决方法2:使用通知机制

在B控制器中发送通知：

//SecondViewController.m
- (IBAction)notificationMethod:(id)sender {
    if ([self notEmpty]) {
        [[NSNotificationCenter defaultCenter] postNotificationName:@"ChangeNameNotification" object:self userInfo:@{@"name":self.nameTextField.text}];
        [self dismissViewControllerAnimated:YES completion:nil];
    }else{
        [self showAlert];
    }
}

在A控制器中注册通知：

//RootViewController.m
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(ChangeNameNotification:) name:@"ChangeNameNotification" object:nil];
}

记得在不使用的时候一定要移除通知，不然会造成内存泄露

//RootViewController.m
-(void)dealloc{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

调用显示：

//RootViewController.m
 
-(void)ChangeNameNotification:(NSNotification*)notification{
    NSDictionary *nameDictionary = [notification userInfo];
    self.nameLabel.text = [nameDictionary objectForKey:@"name"];
}

解决方法3：使用Block去实现

在B控制器中内定义一个Block，参数为string

typedef void (^aBlock)(NSString *str)

@property(nonamatic,copy) aBlock block;

在B控制器中:

- (IBAction)blockMethod:(id)sender {
    if ([self notEmpty]) {
        if (self.block) {
            self.block(self.nameTextField.text);
            [self dismissViewControllerAnimated:YES completion:nil];
        }
    }else{
        [self showAlert];
    }
}

在A视图显示，回调Block

- (IBAction)showSecondWithBlock:(id)sender {
    SecondViewController *second = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
    [self presentViewController:second animated:YES completion:nil];
    second.block = ^(NSString *str){
        self.nameLabel.text = str;
    };
}

单例模式传值的话，感觉有那么点别扭，这里就不作介绍啦！