block傳值

                              block傳值

事實上block傳值我的感受跟代理很是類似.也是從後往前傳.

//流程:
1.後一個界面定義一個block,並且定義一個屬性block
2.在後一個界面返回前一個界面的瞬間,(即:建立完畢一個界面以後),調用block;
3.前一個界面實現block的實現
4.後一個界面在合適的機會, 讓(傳的值以參數的形式 含在block的參數裏)

代碼例如如下:

<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 = @"首頁";
    self.view.userInteractionEnabled = YES;
    /**
     *  1.建立一個UIButton,
     *  2.並加入響應事件,從首頁跳轉到第二個頁面.
     */
    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個界面建立一個UILabel
     *  2.把第二頁輸入框輸入的字符串,經過block內部實現傳過來
     *  3.而後經過賦值給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的方法推出下一個頁面
     *  2.把第二頁輸入框輸入的字符串,經過block內部實現傳過來
     *  3.從而實現把輸入框輸入的字符串,傳到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;//建立一個輸入框
}
@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 = @"第二頁";
    /**
     *  1.建立一個UIButton,
     *  2.並加入響應事件,從第二個頁面返回到首頁.
     */
    UIButton * button = [UIButton systemButtonWithFrame:CGRectMake(100, 120, 50, 50) title:@"Back" target:self action:@selector(didClickButtonAction)];
    [self.view addSubview:button];
    
    /**
     *  1.在第二個界面建立一個輸入框
     *
     */
    _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
{

   //調用block方法,把<span style="font-family: Arial;">_textField.text做爲參數傳過去</span>

    _blocks(_textField.text);
    [self.navigationController popToRootViewControllerAnimated:YES];
}

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

@end