#import <UIKit/UIKit.h> @interface AppDelegate : UIResponder <UIApplicationDelegate> @property (strong, nonatomic) UIWindow *window; @end
#import "AppDelegate.h"
#import "RootViewController.h"
@interface AppDelegate () @end @implementation AppDelegate - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.backgroundColor = [UIColor whiteColor];
// 给根控制器添加导航栏
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:[[RootViewController alloc] init]];
self.window.rootViewController = navigationController; [self.window makeKeyAndVisible];
return YES;
} @end
#import <UIKit/UIKit.h> @interface RootViewController : UIViewController @end
#import "RootViewController.h"
#import "BViewController.h"
@interface RootViewController ()
{
BViewController *bVC;
}
@end @implementation RootViewController - (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor whiteColor];
// 初始化button
UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
btn.frame = CGRectMake(, , , );
btn.backgroundColor = [UIColor greenColor];
[btn setTitle: @"PUSH到下一个控制器" forState:];
[btn setTitleColor:[UIColor orangeColor] forState:];
[btn addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:btn];
//初始化label
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(, , , )];
label.backgroundColor = [UIColor redColor];
label.textColor = [UIColor yellowColor];
[self.view addSubview:label];
//初始化BViewController
bVC = [[BViewController alloc] init]; // 声明block(注意：这里只是声明，并没有执行block的代码，只有当block被调用才执行下面的代码)
bVC.titleString = ^(NSString *title){
label.text = title;
};
} - (void)btnAction:(UIButton *)sender{
// push到下一个控制器
[self.navigationController pushViewController:bVC animated:YES];
} @end
#import <UIKit/UIKit.h> typedef void(^titleBlock)(NSString *showText); @interface BViewController : UIViewController
// 注意：copy 把block从栈区推到堆区
@property (nonatomic, copy) titleBlock titleString; @end
#import "BViewController.h" @interface BViewController ()
{
UITextField *tf;
}
@end @implementation BViewController - (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor whiteColor];
// 初始化tf
tf = [[UITextField alloc] initWithFrame:CGRectMake(, , , )];
tf.backgroundColor = [UIColor lightGrayColor];
tf.text = @"把值传到根控制器";
tf.textColor = [UIColor yellowColor];
[self.view addSubview:tf];
}
/**
* 当页面将要消失时，传值到根控制器
*/
- (void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
if (tf.text.length != ) {
//执行block的代码（当执行此语句，就会跳到RootViewController的block声明的地方，执行block的代码）
self.titleString(tf.text);
}
} @end