使用Block逆向传值

1.ViewController.m

#import "ViewController.h"
#import "MyViewController.h"

/**
 * 逆向传值：A（ViewController）跳转B（MyViewController.h），当点击B时，将B的某个值传给A
 */

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    MyViewController *vc = [[MyViewController alloc] init];
    vc.view.backgroundColor = [UIColor brownColor];

    //block赋值
    vc.block = ^(NSString *value)
    {
        NSLog(@"%@",value);
    };
    [self presentViewController:vc animated:YES completion:nil];
}

2.MyViewController.m

#import "MyViewController.h"

@interface MyViewController ()

@end

@implementation MyViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}


- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    self.block(@"hello");
}