block块简单传值

在NextViewController.h里边声明

#import <UIKit/UIKit.h>

typedef void( ^myBlock) (NSString *str);


@interface NextViewController : UIViewController
@property(nonatomic,copy)NSString *stringTextfield;

@property(nonatomic,copy)myBlock mb;


@end

在NextViewController.m里边

#import "NextViewController.h"
#import "NextView.h"
@interface NextViewController ()
@property(nonatomic,strong)NextView *nv;
@end

@implementation NextViewController


-(void)dealloc{
    //如果是MRC下.加上这句话
   // Block_release(_mb);
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
        self.nv=[[NextView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    }
    return self;
}
-(void)loadView{
    self.view=self.nv;
}
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    UIBarButtonItem *barz=[[UIBarButtonItem alloc] initWithTitle:@"退回" style:UIBarButtonItemStyleDone target:self action:@selector(tuiAction:)];
    self.navigationItem.leftBarButtonItem=barz;
    self.nv.textField.text=self.stringTextfield;
    
}

-(void)tuiAction:(UIBarButtonItem *)sender{
 
    
    self.mb(self.nv.textField.text);
  
    [self.navigationController popViewControllerAnimated:YES];

}


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end

在RootViewController里边的Button事件里边

-(void)barAction:(UIBarButtonItem *)sender{

    NextViewController *nc=[[NextViewController alloc] init];
//    //weakself可以再block块中修改

    __weak RootViewController *weakSelf=self;
    nc.mb=^(NSString *str){
    
    weakSelf.rv.textField.text=str;
    };
    
    
    
    
    nc.stringTextfield=self.rv.textField.text;
    [self.navigationController pushViewController:nc animated:YES];


}