63.delegate回调 和block回调

效果：viewController里面放置一个按钮和Lab，点击按钮进入oneViewController（delegate回调）或者BlockViewController（block回调），两者控制器里面分别有一个输入框，输入文字后 点击完成，把文本框输入的内容回调到  VIewController里面的 Lab上显示出来!

第一种：delegate回调

1.首先在oneViewController.h里面声明代理

#import <UIKit/UIKit.h>

//协议

@protocol OneViewDelegate

//代理方法

-(void)returnFieldText:(NSString*)string;

@end

@interface OneViewController : UIViewController

//声明属性

@property(nonatomic,strong)id <OneViewDelegate>delegate;

@end

2.实现代理

#import "OneViewController.h"

@interface OneViewController ()

@property(nonatomic,strong)UITextField *textField;

@end

@implementation OneViewController

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor=[UIColor whiteColor];

self.textField = [[UITextField alloc] initWithFrame:CGRectMake(100, 100, 100, 30)];

self.textField.backgroundColor = [UIColor greenColor];

[self.view addSubview:self.textField];

UIBarButtonItem *rightButton = [[UIBarButtonItem alloc] initWithTitle:@"完成" style:UIBarButtonItemStylePlain target:self action:@selector(doRightButtonAction)];

self.navigationItem.rightBarButtonItem = rightButton;

}

-(void)doRightButtonAction{

NSLog(@"这是第二步");

[self.delegate returnFieldText:self.textField.text];

[self.navigationController popViewControllerAnimated:YES];

}

3. 在ViewController回调

#import "ViewController.h"

#import "OneViewController.h"

@interface ViewController ()<BlockViewDelegate>

@property(nonatomic,strong)UILabel *lab;

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor=[UIColor whiteColor];

UIButton *btn=[UIButton buttonWithType:UIButtonTypeCustom];

btn.frame=CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height);

[btn addTarget:self action:@selector(back) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:btn];

self.lab=[[UILabel alloc]initWithFrame:CGRectMake(0, 80, 200, 50)];

self.lab.backgroundColor=[UIColor redColor];

[self.view addSubview:self.lab];

}

-(void)back{

OneViewController *one=[[OneViewController alloc]init];

one.delegate = self; （注意：控制器入栈，这个必须写）

[self.navigationController pushViewController:one animated:YES];

}

//代理回调

-(void)returnFieldText:(NSString *)string{

NSLog(@"这是第3");

[self.lab setText:string];

}

第二种 Block回调

1.声明block

#import <UIKit/UIKit.h>

//声明别名ReturnTextWithBlock

typedef void (^ReturnTextWithBlock)(NSString *text);

@interface BlockViewController : UIViewController

//属性

（注意：block修饰必须用copy，不然会出问题）

@property(nonatomic,copy)ReturnTextWithBlock  returnTextBlock;

//方法

-(void)returnTextFieldWithBlock:(ReturnTextWithBlock)block;

@end

2.实现ReturnTextWithBlock

#import "BlockViewController.h"

@interface BlockViewController ()

@property(nonatomic,strong)UITextField *textField;

@end

@implementation BlockViewController

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor=[UIColor whiteColor];

self.textField = [[UITextField alloc] initWithFrame:CGRectMake(100, 100, 100, 30)];

self.textField.backgroundColor = [UIColor greenColor];

[self.view addSubview:self.textField];

UIBarButtonItem *rightButton = [[UIBarButtonItem alloc] initWithTitle:@"完成" style:UIBarButtonItemStylePlain target:self action:@selector(doRightButtonAction)];

self.navigationItem.rightBarButtonItem = rightButton;

}

-(void)doRightButtonAction{

NSLog(@"第2");

self.returnTextBlock(self.textField.text);

[self.navigationController popViewControllerAnimated:YES];

}

-(void)returnTextFieldWithBlock:(ReturnTextWithBlock)block{

NSLog(@"第1");

block是存在栈区的，随着viewDidLoad消失会消失，我们要操作 将它放入堆区，赋值  引用计数加1 ，不会导致中途丢失

self.returnTextBlock = block;

}

3.回调实现block

#import "ViewController.h"

#import "BlockViewController.h"

@interface ViewController ()

@property(nonatomic,strong)UILabel *lab;

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor=[UIColor whiteColor];

UIButton *btn=[UIButton buttonWithType:UIButtonTypeCustom];

btn.frame=CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height);

[btn addTarget:self action:@selector(back) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:btn];

self.lab=[[UILabel alloc]initWithFrame:CGRectMake(0, 80, 200, 50)];

self.lab.backgroundColor=[UIColor redColor];

[self.view addSubview:self.lab];

}

-(void)back{

BlockViewController *BlockVC=[[BlockViewController alloc]init];

__weak typeof (self)weakSelf = self;

//回调block

[BlockVC returnTextFieldWithBlock:^(NSString *text) {

[weakSelf.lab setText:text];

}];

[self.navigationController pushViewController:BlockVC animated:YES];

}

@end

传值的话：还有属性，通知等传值方式