iOS 使用Block进行逆传值

跟通知一样也是两个控制器,然后代码创建控件直接上代码

#import "ViewController.h"

#import "TwoViewController.h"

@interface ViewController ()

{

UIButton *_nextBtn;

UILabel *_showLabel;

}

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

[self show];

}

-(void)show{

_nextBtn = [[UIButton alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];

[_nextBtn setTitleColor:[UIColor redColor] forState:UIControlStateNormal];

[_nextBtn setTitle:@"下一个" forState:UIControlStateNormal];

[_nextBtn addTarget:self action:@selector(nextBtnClick:) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:_nextBtn];

_showLabel = [[UILabel alloc]initWithFrame:CGRectMake(100, 300, 100,50)];

[_showLabel setBackgroundColor:[UIColor greenColor]];

[_showLabel setTextColor:[UIColor redColor]];

[self.view addSubview:_showLabel];

}

-(void)nextBtnClick:(UIButton *)nextBtnClick{

TwoViewController * two = [[TwoViewController alloc]init];

two.block = ^(NSString * str){

_showLabel.text = str;

};

[self presentViewController:two animated:YES completion:nil];

}

在TwoViewController.h中

#import <UIKit/UIKit.h>

typedef void (^MyBlock)(NSString *);

@interface TwoViewController : UIViewController

@property(nonatomic,copy)MyBlock block;

@end

在TwoViewController.m中

#import "TwoViewController.h"

@interface TwoViewController ()

{

UIButton *_backBtn;

UITextField *_textField;

}

@end

@implementation TwoViewController

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor = [UIColor blueColor];

[self shoulabel];

}

-(void)shoulabel{

_backBtn = [[UIButton alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];

_backBtn.backgroundColor = [UIColor redColor];

[_backBtn setTitle:@"shang" forState:UIControlStateNormal];

[_backBtn addTarget:self action:@selector(shangBtnClick:) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:_backBtn];

_textField = [[UITextField alloc]initWithFrame:CGRectMake(100, 400, 250, 35)];

_textField.backgroundColor = [UIColor yellowColor];

[self.view addSubview: _textField];

}

-(void)shangBtnClick:(UIButton *)shangBtn{

[self dismissViewControllerAnimated:YES completion:^{

if (self.block) {

self.block(_textField.text);

}

}];

}

这样就进行了简单的传值