IOS传值之Block传值（二）

@interface QWViewController : UIViewController

@property(nonatomic,strong)UILabel *label;

@property(nonatomic,strong)UITextField *textField;

@end

#import "QWViewController.h"

#import "QWViewControllerTwo.h"

@interface QWViewController ()

@end

@implementation QWViewController

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view.

UILabel *label=[[UILabel alloc]initWithFrame:CGRectMake(100, 100, 100, 50)];

label.backgroundColor=[UIColor blueColor];

self.label=label;

[self.view addSubview:label];

UITextField *textField=[[UITextField alloc]initWithFrame:CGRectMake(100, 200, 100, 50)];

textField.backgroundColor=[UIColor yellowColor];

self.textField=textField;

[self.view addSubview:textField];

UIButton *button=[UIButton buttonWithType:UIButtonTypeCustom];

button.frame=CGRectMake(100, 300, 100, 50);

button.backgroundColor=[UIColor blackColor];

[button setTitle:@"jump" forState:UIControlStateNormal];

[button addTarget:self action:@selector(doClicked) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:button];

}

-(void)doClicked{

QWViewControllerTwo *ViewControllerTwo=[[QWViewControllerTwo alloc]init];

ViewControllerTwo.labelText=self.textField.text;//顺传值

//[ViewControllerTwo.label setText:self.textField.text];//注意：这样传值是不对的。

//逆向传值回来

[ViewControllerTwo returnText:^(NSString *showText) {

self.label.text=showText;

}];

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

}

- (void)didReceiveMemoryWarning {

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end

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#import <UIKit/UIKit.h>

typedef void(^ReturnTextBlock) (NSString *showText);

@interface QWViewControllerTwo : UIViewController

@property(nonatomic,copy)NSString *labelText;

@property(nonatomic,strong)UILabel *label;

@property(nonatomic,strong)UITextField *textField;

@property(nonatomic,copy)ReturnTextBlock returnTextBlock;

-(void)returnText:(ReturnTextBlock)block;

@end

#import "QWViewControllerTwo.h"

@interface QWViewControllerTwo ()

@end

@implementation QWViewControllerTwo

-(UILabel *)label{

if (_label==nil) {

_label=[[UILabel alloc]initWithFrame:CGRectMake(100, 100, 100, 50)];

}

return _label;

}

-(UITextField *)textField{

if (_textField==nil) {

_textField=[[UITextField alloc]initWithFrame:CGRectMake(100, 200, 100, 50)];

}

return _textField;

}

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view.

UILabel *label=[[UILabel alloc]initWithFrame:CGRectMake(100, 100, 100, 50)];

label.backgroundColor=[UIColor yellowColor];

label.text=self.labelText;

self.label=label;

[self.view addSubview:self.label];

UITextField *textField=[[UITextField alloc]initWithFrame:CGRectMake(100, 200, 100, 50)];

textField.backgroundColor=[UIColor yellowColor];

self.textField=textField;

[self.view addSubview:textField];

//创建返回按钮

UIButton *backBtn=[UIButton buttonWithType:UIButtonTypeCustom];

[backBtn addTarget:self action:@selector(goBack) forControlEvents:UIControlEventTouchUpInside];

[backBtn setTitle:@"back" forState:UIControlStateNormal];

}

-(void)goBack{

[self.navigationController popViewControllerAnimated:YES];

}

//将上一个控制器传过来的block保存在本控制器中，在合适的时候调用

-(void)returnText:(ReturnTextBlock)block{

self.returnTextBlock=block;

}

//在视图将要消失的时候调用本类的block

-(void)viewWillDisappear:(BOOL)animated{

if (self.returnTextBlock !=nil) {

self.returnTextBlock(self.textField.text);//实现是在之前控制器中

}

}

@end

实现效果：