1.属性传值和协议传值
1 #import "RootViewController.h"
2 #import "SecondViewController.h"
3 #warning 第四步:签订协议
4 @interface RootViewController ()<SecondViewControllerDelegate>
5 @property(nonatomic,strong)UILabel *showTextLable;
6 @end
7
8 @implementation RootViewController
9
10 - (void)viewDidLoad {
11 [super viewDidLoad];
12 // Do any additional setup after loading the view.
13 self.view.backgroundColor = [UIColor whiteColor];
14 self.navigationItem.title = @"首页";
15 //创建UILable用于显示内容
16 UILabel *showTextLable = [[UILabel alloc] initWithFrame:CGRectMake(100, 200, 150, 50)];
17 showTextLable.backgroundColor = [UIColor yellowColor];
18 showTextLable.text = @"美女帅哥";
19 showTextLable.textAlignment = NSTextAlignmentCenter;
20 [self.view addSubview:showTextLable];
21 self.showTextLable = showTextLable;
22
23 //创建推出下个界面的UIButton
24 UIButton *pushNextBtn = [UIButton buttonWithType:UIButtonTypeCustom];
25 pushNextBtn.frame = CGRectMake(100, 300, 150, 50);
26 pushNextBtn.backgroundColor = [UIColor magentaColor];
27 [pushNextBtn setTitle:@"下一页" forState:UIControlStateNormal];
28 [pushNextBtn addTarget:self action:@selector(pushNextController) forControlEvents:UIControlEventTouchUpInside];
29 [self.view addSubview:pushNextBtn];
30
31
32 }
33 -(void)pushNextController
34 {
35 SecondViewController *secondVC = [[SecondViewController alloc] init];
36 //需要把lable的text传给
37 //下面这种传值方法是错误的,因为textField还没有创建,还没有加载到视图上,这里是项目期特别容易犯错的地方,必须要考虑视图加载的顺序
38 //secondVC.textField.text = self.showTextLable.text;
39 //正确的写法应该是直接传送文本内容
40 secondVC.content = self.showTextLable.text;
41 //
42 #warning 第五步:指定代理人
43 secondVC.secondViewControllerDelegate = self;//指定协议代理人
44 [self.navigationController pushViewController:secondVC animated:YES];
45 }
46 #warning 第六步:实现协议的方法
47 -(void)changeValue:(NSString *)text
48 {
49 self.showTextLable.text = text;
50 }
51 - (void)didReceiveMemoryWarning {
52 [super didReceiveMemoryWarning];
53 // Dispose of any resources that can be recreated.
54 }
1 #import <UIKit/UIKit.h> 2 #warning 第一步:声明协议 3 @protocol SecondViewControllerDelegate <NSObject> 4 5 -(void)changeValue:(NSString *)text; 6 @optional//可选的协议方法 7 -(void)changeColor:(UIColor *)color; 8 9 @end 10 @interface SecondViewController : UIViewController 11 /** 12 * 显示文本输入框的 13 */ 14 @property (nonatomic,strong) UITextField *textField; 15 /** 16 * 显示文本输入框的内容文本 17 */ 18 @property (nonatomic,strong) NSString *content; 19 #warning 第二步:声明代理人 20 /** 21 * 第二个Controller中的协议, 22 assign必须循环引用 23 */ 24 @property (nonatomic,assign)id<SecondViewControllerDelegate>secondViewControllerDelegate; 25 @end
1 #import "SecondViewController.h"
2
3 @interface SecondViewController ()
4
5 @end
6
7 @implementation SecondViewController
8
9 - (void)viewDidLoad {
10 [super viewDidLoad];
11 // Do any additional setup after loading the view.
12 self.view.backgroundColor = [UIColor whiteColor];
13 self.navigationItem.title= @"第二页";
14 //创建输入文本的文本框
15 UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(100, 200, 150, 50)];
16 textField.placeholder = @"请输入文本内容";
17 textField.borderStyle = UITextBorderStyleRoundedRect;
18 [self.view addSubview:textField];
19 self.textField = textField;
20 self.textField.text = self.content;
21
22 //创建UIButton用于返回上一个界面
23 UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
24 backBtn.frame = CGRectMake(100, 300, 150, 50);
25 [backBtn setTitle:@"返回" forState:UIControlStateNormal];
26 backBtn.backgroundColor = [UIColor blackColor];
27 [backBtn addTarget:self action:@selector(popButtonAction) forControlEvents:UIControlEventTouchUpInside];
28 [self.view addSubview:backBtn];
29
30
31 }
32 -(void)popButtonAction
33 {
34 #warning 第三步:执行相关的协议方法
35 [self.secondViewControllerDelegate changeValue:self.textField.text];
36 [self.navigationController popViewControllerAnimated:YES];
37 }
38 //总结:属性传值:一般使用从前往后进行传值的情况
39 //如果从后往前,需要借助其他传值方式
40 //协议传值方式
41 /**
42 * 实现协议的六个步骤:
43 第一步:声明协议
44 第二步:声明代理人
45 第三步:执行协议方法
46 第四步:签订协议
47 第五步:指定代理人
48 第六步:实现协议方法
49 */
2.Block传值
1 #import "RootViewController.h"
2 #import "SecondViewController.h"
3 @interface RootViewController ()
4 @property(nonatomic,strong)UILabel *showTextLable;
5 @end
6
7 @implementation RootViewController
8
9 - (void)viewDidLoad {
10 [super viewDidLoad];
11 // Do any additional setup after loading the view.
12 UILabel *showLabel = [[UILabel alloc] initWithFrame:CGRectMake(100, 200, 150, 50)];
13 showLabel.backgroundColor = [UIColor redColor];
14 showLabel.text = @"美女帅哥";
15 showLabel.textAlignment = NSTextAlignmentCenter;
16 showLabel.font = [UIFont systemFontOfSize:24];
17 [self.view addSubview:showLabel];
18 self.showTextLable = showLabel;
19 UIButton *nextBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
20 nextBtn.frame = CGRectMake(100, 300, 150, 50);
21 nextBtn.backgroundColor = [UIColor yellowColor];
22 [nextBtn setTitle:@"下一页" forState:UIControlStateNormal];
23 [nextBtn addTarget:self action:@selector(showNextAction) forControlEvents:UIControlEventTouchUpInside];
24 [self.view addSubview:nextBtn];
25
26 }
27 -(void)showNextAction
28 {
29 SecondViewController *secondView = [[SecondViewController alloc] init];
30 [self.navigationController pushViewController:secondView animated:YES];
31 //ARC模式下用__weak修饰可解决内存泄漏问题,MRC模式下用__block
32 __weak typeof (self)weakSelf = self;
33 #warning 第三步:实现Block的内容(实现传递过来的内容)
34 secondView.changeValueBlock = ^(NSString *string){
35 //下面这种引用容易造成内存泄漏
36 //self.showTextLable.text = string;
37 weakSelf.showTextLable.text = string;
38 };
39 //block的核心是:回调,Block作为属性进行传值的时候,一般使用场景是从第二个界面返回到上一个界面,基本步骤:
40 //1.在第二个界面中声明一个Block属性
41 //2.在第二个界面返回的那句代码之前加上Block需要传递的内容
42 //3.在一个界面推出第二个界面那句代码之前,对Block进行实现(即接受Block传递过来的内容)
43 secondView.content = self.showTextLable.text;
44 }
1 #import <UIKit/UIKit.h> 2 3 @interface SecondViewController : UIViewController 4 @property (nonatomic,strong) NSString *content; 5 @property (strong,nonatomic) UITextField *textField; 6 #warning 第一步:声明Block属性,copy是为了解决循环引用的问题 7 @property (nonatomic,copy) void(^changeValueBlock)(NSString *string); 8 @end
1 #import "SecondViewController.h"
2
3 @interface SecondViewController ()
4
5 @end
6
7 @implementation SecondViewController
8
9 - (void)viewDidLoad {
10 [super viewDidLoad];
11 // Do any additional setup after loading the view.
12 self.view.backgroundColor = [UIColor whiteColor];
13 self.view.backgroundColor = [UIColor whiteColor];
14 self.navigationItem.title= @"第二页";
15 //创建输入文本的文本框
16 UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(100, 200, 150, 50)];
17 textField.placeholder = @"请输入文本内容";
18 textField.borderStyle = UITextBorderStyleRoundedRect;
19 [self.view addSubview:textField];
20 self.textField = textField;
21 self.textField.text = self.content;
22
23 //创建UIButton用于返回上一个界面
24 UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
25 backBtn.frame = CGRectMake(100, 300, 150, 50);
26 [backBtn setTitle:@"返回" forState:UIControlStateNormal];
27 backBtn.backgroundColor = [UIColor blackColor];
28 [backBtn addTarget:self action:@selector(popButtonAction) forControlEvents:UIControlEventTouchUpInside];
29 [self.view addSubview:backBtn];
30 }
31 -(void)popButtonAction
32 {
33 #warning 第二步:将要传递的内容通过属性block先给它
34 self.changeValueBlock(self.textField.text);
35
36 [self.navigationController popViewControllerAnimated:YES];
37 }
时间： 2024-12-14 21:04:32