KVO---视图间数据的传递：标签显示输入的内容【多个视图中】

#import "ModalViewController.h"

@interface RootViewController ()

@end

@implementation RootViewController {

ModalViewController *modalCtrl;

}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}

- (void)viewDidLoad
{
[super viewDidLoad];

self.view.backgroundColor = [UIColor redColor];

UILabel *textLabel = [[UILabel alloc] initWithFrame:CGRectMake(50, 100, 200, 20)];
textLabel.tag = 100;
textLabel.backgroundColor = [UIColor orangeColor];
[self.view addSubview:textLabel];

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
button.frame = CGRectMake(50, 150, 100, 30);
[button setTitle:@"打开" forState:UIControlStateNormal];
[button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];

modalCtrl = [[ModalViewController alloc] init];

//监听modal控制器的text属性
[modalCtrl addObserver:self forKeyPath:@"text"
options:NSKeyValueObservingOptionNew
context:NULL];

}

//KVO触发方法
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

if ([keyPath isEqualToString:@"text"]) {

NSString *text = [change objectForKey:@"new"];
UILabel *label = (UILabel *)[self.view viewWithTag:100];
label.text = text;

}

}

- (void)buttonAction
{
[self presentViewController:modalCtrl animated:YES completion:NULL];

}

@interface ModalViewController ()
{
NSString *_text;
}
@end

@implementation ModalViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}

- (void)viewDidLoad
{
[super viewDidLoad];

self.view.backgroundColor = [UIColor greenColor];

UITextField *textFiled = [[UITextField alloc] initWithFrame:CGRectMake(50, 60, 160, 30)];
textFiled.tag = 100;
textFiled.delegate = self;
textFiled.borderStyle = UITextBorderStyleRoundedRect;
[self.view addSubview:textFiled];
//显示键盘
[textFiled becomeFirstResponder];

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
button.frame = CGRectMake(50, 150, 100, 30);
[button setTitle:@"返回" forState:UIControlStateNormal];
[button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];

}

//按钮点击事件
- (void)buttonAction
{
[self dismissViewControllerAnimated:YES completion:NULL];

//    UITextField *field = (UITextField *)[self.view viewWithTag:100];
//    NSString *text = field.text;

//    self.text = text;

}

#pragma UITextField delegate

//点击return调用的协议方法
- (BOOL)textFieldShouldReturn:(UITextField *)textField {

//收起键盘
[textField resignFirstResponder];

return YES;

}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

NSLog(@"string:%@",string);
//    string 是正在输入的最后一个字符

NSLog(@"%@",textField.text);
//    textField.text 是输入的内容的前段字符（最后一个字符不包括）

//    UITextField *field = (UITextField *)[self.view viewWithTag:100];
//    NSString *text = field.text;
NSString *str = [NSString stringWithFormat:@"%@%@",textField.text,string];
NSLog(@"str:%@",str);
self.text = str;

return YES;

}