属性传值与代理传值

MVC通过控制中心C来完成信息的传递。常用的方式有，属性传值、代理传值、单例传值以及通过通知中心传值。

视图对象负责展示数据，通常它不会存储数据。数据存储在控制器中，视图通常会让控制器成为自己的委托，在显示数据时调用其委托中相应地方法。

为了降低类之间的耦合度，经常使用委托模式来进行传值。委托模式涉及到协议。

如下例子：

协议

#import <Foundation/Foundation.h>

@protocol ModifyTitleDelegate <NSObject>

- (void)modifyTitle:(NSString *)title;

@end

AViewController

#import <UIKit/UIKit.h>

#import "ModifyTitleDelegate.h"

@interface AViewController : UIViewController<ModifyTitleDelegate>

@end

#import "AViewController.h"

#import "BViewController.h"

@interface AViewController ()

@end

@implementation AViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    if (self) {

    }

    return self;

}

- (void)viewDidLoad

{

    [super viewDidLoad];

    UIButton *btnTest = [UIButton buttonWithType:UIButtonTypeRoundedRect];

    [btnTest setTitle:@"PUSH" forState:UIControlStateNormal];

    btnTest.frame = CGRectMake(0, 0, 80, 30);

    btnTest.center = self.view.center;

    [btnTest addTarget:self action:@selector(pushToNext) forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:btnTest];

}

- (void)pushToNext{

    BViewController *secondVC = [[BViewController alloc] init];

    //属性传值

    secondVC.title = @"Second";

    //设置代理

    secondVC.delegate = self;

    

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

    

}

- (void)modifyTitle:(NSString *)title

{

    self.title = title;

}

- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

}

@end

BViewController

#import <UIKit/UIKit.h>

#import "ModifyTitleDelegate.h"

@interface BViewController : UIViewController

@property (assign, nonatomic) id <ModifyTitleDelegate>delegate;

@property (retain, nonatomic) UITextField *myTextField;

@end

#import "BViewController.h"

@interface BViewController ()

@end

@implementation BViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    if (self) {

    }

    return self;

}

- (void)viewDidLoad

{

    [super viewDidLoad];

    UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];

    [btn setTitle:@"Test" forState:UIControlStateNormal];

    btn.frame = CGRectMake(120, 130, 80, 30);

    [btn addTarget:self action:@selector(btnPressed) forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:btn];

    

    self.myTextField = [[UITextField alloc] initWithFrame:CGRectMake(120, 80, 80, 30)];

    self.myTextField.borderStyle = UITextBorderStyleRoundedRect;

    [self.view addSubview:self.myTextField];

}

- (void)btnPressed

{

    //代理传值

    [self.delegate modifyTitle:self.myTextField.text];

    [self.navigationController popToRootViewControllerAnimated:YES];

    

}

- (void)dealloc

{

    [_myTextField release];

    [super dealloc];

}

- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

}

@end