block传值

其实block传值个人感觉跟代理很相似.也是从后往前传.

//流程:
1.后一个界面定义一个block,并且定义一个属性block
2.在后一个界面返回前一个界面的瞬间,(即:创建完成一个界面之后),调用block;
3.前一个界面实现block的实现
4.后一个界面在合适的机会, 让(传的值以参数的形式 含在block的参数里)

代码如下:

<pre name="code" class="objc">#import "FirstViewController.h"#import "SecondViewController.h"#import "UIButton+Create.h"@interface FirstViewController (){    UILabel * _label;}@end@implementation FirstViewController- (void)dealloc{    [_label release];    [super dealloc];}- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];    if (self) {        // Custom initialization    }    return self;}- (void)viewDidLoad{    [super viewDidLoad];    self.view.backgroundColor = [UIColor redColor];    self.navigationItem.title = @"首页";    self.view.userInteractionEnabled = YES;    /**     *  1.创建一个UIButton,     *  2.并添加响应事件,从首页跳转到第二个页面.     */    UIButton * button = [UIButton systemButtonWithFrame:CGRectMake(100, 120, 50, 50) title:@"Push" target:self action:@selector(didClickButtonAction)];    button.userInteractionEnabled = YES;    [self.view addSubview:button];                /**     *  1.在第1个界面创建一个UILabel     *  2.把第二页输入框输入的字符串,通过block内部实现传过来     *  3.然后通过赋值给UILabel     */    _label = [[UILabel alloc]initWithFrame:CGRectMake(50, 80, 200, 30)];    _label.backgroundColor = [UIColor greenColor];    [self.view addSubview:_label];    // Do any additional setup after loading the view.}- (void)didClickButtonAction{        /**     *  1.用push的方法推出下一个页面     *  2.把第二页输入框输入的字符串,通过block内部实现传过来     *  3.从而实现把输入框输入的字符串,传到UILabel上.     */    SecondViewController * secondVC = [[SecondViewController alloc]init];    secondVC.blocks=^(NSString * str){                 _label.text = str;    };    [self.navigationController pushViewController:secondVC animated:YES];    [secondVC release];}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end

<pre name="code" class="objc">#import <UIKit/UIKit.h>typedef void(^block)(NSString * str) ;@interface SecondViewController : UIViewController@property (nonatomic,copy)block blocks;@end

#import "SecondViewController.h"#import "UIButton+Create.h"#import "FirstViewController.h"@interface SecondViewController (){    UITextField * _textField;//创建一个输入框}@end@implementation SecondViewController- (void)dealloc{    [_textField release];    [super dealloc];}- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];    if (self) {        // Custom initialization    }    return self;}- (void)viewDidLoad{    [super viewDidLoad];    self.view.backgroundColor = [UIColor orangeColor];    self.navigationItem.title = @"第二页";    /**     *  1.创建一个UIButton,     *  2.并添加响应事件,从第二个页面返回到首页.     */    UIButton * button = [UIButton systemButtonWithFrame:CGRectMake(100, 120, 50, 50) title:@"Back" target:self action:@selector(didClickButtonAction)];    [self.view addSubview:button];        /**     *  1.在第二个界面创建一个输入框     *     */    _textField = [[UITextField alloc]initWithFrame:CGRectMake(50, 80, 200, 30)];    _textField.borderStyle = UITextBorderStyleRoundedRect;    [self.view addSubview:_textField];            // Do any additional setup after loading the view.}- (void)didClickButtonAction{

   //调用block方法,把<span style="font-family: Arial;">_textField.text作为参数传过去</span>    _blocks(_textField.text);    [self.navigationController popToRootViewControllerAnimated:YES];}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end