KVO

ViewController.m

#import "ViewController.h"
#import "Student.h"
#import "SecondViewController.h"
@interface ViewController ()

@property(nonatomic, retain)Student *stu;
@property(nonatomic, retain)UITextField *textField;

@end

@implementation ViewController

- (void)viewDidLoad {
//  KVC  Key - Value - Coding
//  KVO  Key - Value - Observer 键值观察者.监控属性的值得变化,只要变化就会触发相应的操作.

self.stu = [[Student alloc] init];

// 注册一个观察者
// 参数1:给对象添加一个观察者,就是当前类的对象self.
// 参数2:需要监控的属性名.
// 参数3:触发的条件,旧内容变成新内容就会触发.
[self.stu addObserver:self forKeyPath:@"name" options:NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew context:@"监控的文本"];

self.stu.name = @"韩老师";

用此方法来监控目标对象.
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
NSLog(@"%@", change[@"new"]);
NSLog(@"%@", keyPath);
}

1.传值的第四种方式:通知中心也叫消息中心.
UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
button.frame = CGRectMake(100, 100, 100, 50);
button.backgroundColor = [UIColor yellowColor];
[button setTitle:@"前往" forState:UIControlStateNormal];
[button addTarget:self action:@selector(goClick:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];

// 给通知中心加上一个观察者.
// 参数1:添加一个观察者.
// 参数2:需要绑定一个方法.
// 参数3:给name起一个名.

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(backValue:) name:@"test" object:nil];

按钮绑定的方法.
- (void)goClick:(UIButton *)button {
SecondViewController *secondVC  = [[SecondViewController alloc] init];
[secondVC setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
[self presentViewController:secondVC animated:YES completion:^{

}];
[secondVC release];
}

打印通知中心传回来的字典.
- (void)backValue:(NSNotification *)notification {
NSLog(@"%@", notification.userInfo);
}

SecondViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
self.view.backgroundColor = [UIColor cyanColor];

UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
button.frame = CGRectMake(100, 100, 100, 50);
button.backgroundColor = [UIColor greenColor];
[button setTitle:@"返回" forState:UIControlStateNormal];
[button addTarget:self action:@selector(backClick:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];
}

- (void)backClick:(UIButton *)button {

// 把值进行返回.
[[NSNotificationCenter defaultCenter] postNotificationName:@"test" object:nil userInfo:@{@"1":@"2"}];

[self dismissViewControllerAnimated:YES completion:^{
}];
}

self.textField = [[UITextField alloc] initWithFrame:CGRectMake(100, 200, 150, 50)];
self.textField.backgroundColor = [UIColor greenColor];
[self.view addSubview:self.textField];
[_textField release];
self.textField.layer.borderWidth = 1;
self.textField.layer.cornerRadius = 10;

2.第一种:监听textField输入内容的方法.
[self.textField addTarget:self action:@selector(changeValue:) forControlEvents:UIControlEventEditingChanged];

监控文本框的输入内容,正在编辑.
- (void)changeValue:(UITextField *)textField {
NSLog(@"%@", textField.text);
}

3.第二种:通过通知中心监听textField的内容,编辑完成.
//     参数3:在textField头文件的最后几行
//     参数4:要监听的对象
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(value:) name:UITextFieldTextDidChangeNotification object:self.textField];

编辑完成的方法,用正则表达式和谓词.
- (void)value:(NSNotification *)natification {
NSLog(@"%@", self.textField.text);

// 这个正则表达式是用来判断一个内容格式是否相符的字符串,正则表达式有自己的语法规则,需要的话,百度.
NSString *str = @"^((13[0-9])|(147)|(15[^4,\\D])|(18[0,5-9]))\\d{8}$";
// 通过谓词来进行内容的比对.
NSPredicate *cate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", str];
if ([cate evaluateWithObject:self.textField.text]) {
NSLog(@"YES");
} else {
NSLog(@"NO");
}
}

- (void)dealloc
{
// ARC下可以写dealloc方法,但是不能写[super dealloc],它需要把观察者从对象上移除掉
[self.stu removeObserver:self forKeyPath:@"name"];
[_stu release];
[super dealloc];
}