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 MineViewController : RSBaseCommonViewController

//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 "TwoViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    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
{
    TwoViewController *newVC = [[TwoViewController alloc] init];
    
    //接收block传来的值
    newVC.block= ^(NSString*str){
        NSLog(@"%@", str);
    };
    
    [self.navigationController pushViewController:newVC animated:YES];
}

@end

④最终实现效果:在控制台打印出了"呵呵"