關於block的傳值

#import <UIKit/UIKit.h>

@interface BViewController : UIViewController

@property(nonatomic,strong)void (^ returnStr) (NSString *str);
- (void)returnStr:(void (^) (NSString *str))str;

@end

 

1.首先要更正自己的一個觀點，屬性爲block函數是能夠被strong修飾的（自己不知道怎麼搞的，一直以爲其職能被assign修飾）

2.那就是關於block的傳值了，直接代碼

在A控制器中 

- (IBAction)tiaoZhuan:(id)sender {

    //A控制器中調用B控制器中帶有block函數的方法

    [self.BVC returnStr:^(NSString *str) {

        self.label.text = str;

        [self.view setNeedsDisplay];

    }];

    [self presentViewController:self.BVC animated:YES completion:nil];

}

在B控制器中 .h文件

#import <UIKit/UIKit.h>

@interface BViewController : UIViewController
//這裏的block屬性需要用strong修飾
@property(nonatomic,strong)void (^ returnStr) (NSString *str);
- (void)returnStr:(void (^) (NSString *str))str;

@end

 .m文件

- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"B-viewDidLoad");
    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
    [button setTitle:@"返回" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(back:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
}

- (void)returnStr:(void (^) (NSString *str))str {
    self.returnStr = str;
    //str(@"我是反回來的");
}

//返回函數
- (void)back:(UIButton *)sender {
    self.returnStr(@"我是反回來的");
    [self dismissViewControllerAnimated:YES completion:nil];
}