【iOS】—— block传值_ios block传值

block传值

block传值和协议传值类似，都是从下一界面往上一界面传值，两者之间在用法上也有着很多相似之处。

第一步

在第二个界面的.h文件里定义一个代码块，和一个block属性。

#import "ViewController.h"

NS_ASSUME_NONNULL_BEGIN
//定义一个代码块，传值参数可以为多个
typedef void(^block)(NSString *string);

@interface SecondViewController : ViewController

@property (nonatomic, strong) NSString *string;
@property (nonatomic, strong) UIButton *button;

//定义一个block属性
@property (nonatomic, copy) block newblock;

@end

NS_ASSUME_NONNULL_END
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第二步

在第二个界面的.h文件里完成按钮的点击事件函数用于返回上一界面，在函数中给block传值：

- (void)pressback {
    _newblock(_string);
    [self dismissViewControllerAnimated:YES completion:nil];
}
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第三步

在第一个界面往二个界面切换的时候，完成对第二个界面传的值进行赋值。

- (void)pressgo {
    SecondViewController *viewcontroller = [[SecondViewController alloc] init];
    viewcontroller.modalPresentationStyle = UIModalPresentationFullScreen;
    
    [viewcontroller setNewblock:^(NSString *string) {
        _label.text = string;
    }];
    
    [self presentViewController:viewcontroller animated:YES completion:nil];
}
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视图一全部代码：

@implementation FirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    _label = [[UILabel alloc] initWithFrame:CGRectMake(200, 200, 100, 100)];
    [self.view addSubview:_label];
    self.view.backgroundColor = [UIColor orangeColor];
    
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [button addTarget:self action:@selector(pressgo) forControlEvents:UIControlEventTouchUpInside];
    button.frame = CGRectMake(0, 0, 200, 200);
    [button setTitle:@"进入" forState:UIControlStateNormal];
    [self.view addSubview:button];
}

- (void)pressgo {
    SecondViewController *viewcontroller = [[SecondViewController alloc] init];
    viewcontroller.modalPresentationStyle = UIModalPresentationFullScreen;
    
    [viewcontroller setNewblock:^(NSString *string) {
        _label.text = string;
    }];
    
    [self presentViewController:viewcontroller animated:YES completion:nil];
}
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视图二全部代码：

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor systemPinkColor];
    
    _button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [_button addTarget:self action:@selector(pressback) forControlEvents:UIControlEventTouchUpInside];
    _button.frame = CGRectMake(0, 0, 200, 200);
    [_button setTitle:@"返回" forState:UIControlStateNormal];
    [self.view addSubview:_button];
    
    _string = [NSString stringWithFormat:@"iOS"];
}

- (void)pressback {
    _newblock(_string);
    [self dismissViewControllerAnimated:YES completion:nil];
}
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结果展示：