iOS使用block从后往前传值

①在后面控制器的 .h文件 中声明block

// 一会要传的值为NSString类型

typedef void (^newBlock)(NSString *);

@interface NewViewController : UIViewController

// 声明block属性

@property (nonatomic, copy) newBlock block;

// 声明block方法

- (void)text:(newBlock)block;

@end

②在后面控制器的 .m文件 中设置block

// 设置block,设置要传的值

- (void)text:(newBlock)block

{

    self.block = block;

}

- (void)viewWillDisappear:(BOOL)animated

{

    [super viewWillDisappear:YES];

    if (self.block != nil) {

        self.block(@"呵呵");

    }

}

③在前面控制器的 .m文件 中接收传来的值

#import "ViewController.h"

#import "NewViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    UIButton *button = [UIButton buttonWithType:(UIButtonTypeRoundedRect)];

    button.frame = CGRectMake(0, 100, 100, 100);

    button.backgroundColor = [UIColor redColor];

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

    [self.view addSubview:button];

}

- (void)push

{

    NewViewController *newVC = [[NewViewController alloc] init];

    // 接收block传来的值

    newVC.block = ^(NSString *str){

        NSLog(@"%@", str);

    };

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

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

@end

④最终实现效果:在控制台打印出了"呵呵"

    到此,block完成传值