使用委托在视图之间传递数据

Question

我正在构建一个实用程序应用程序，它在主视图和翻转视图之间共享数据。实际上，保存数据的并不完全是翻转视图，而是加载时作为翻转视图实例的自定义视图。我已经在之前的帖子此处解释了具体细节，但我还没有找到解决方案。我重新开发了我的代码，希望这次我能说清楚。

这里的一般概念是我在主视图中创建和存储数据，并使用 FlipViewController 中的预定义委托将其传递到翻转视图。然后在 FlipViewController 中，我将数据存储在我自己的委托中，并将其传递给实现我自己的委托方法的自定义视图。以下是代码的主要部分。

MainViewController.m（仅采用协议）

- (IBAction)showInfo:(id)sender {    

    FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:@"FlipsideView" bundle:nil];
    controller.delegate = self;

    controller.chart = data;

    controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
    [self presentModalViewController:controller animated:YES];

    [controller release];
}

FlipsideViewController.h

@protocol FlipsideViewControllerDelegate;
@protocol ChartDelegate;

@interface FlipsideViewController : UIViewController {
    id <FlipsideViewControllerDelegate> delegate;
    id <ChartDelegate> delegate2;
    DataModel *chart;
}

@property (nonatomic, assign) id <FlipsideViewControllerDelegate> delegate;
@property (nonatomic, assign) id <ChartDelegate> delegate2;
@property (nonatomic, retain) DataModel *chart;
- (IBAction)done:(id)sender;
@end


@protocol FlipsideViewControllerDelegate
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
@end

@protocol ChartDelegate <NSObject>
- (void)getParams:(DataModel *)dataModel;
@end

FlipsideViewController.m

@synthesize delegate, delegate2;
@synthesize chart;

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor viewFlipsideBackgroundColor]; 
        if ([delegate2 respondsToSelector:@selector(getParams:)]) {
        [delegate2 getParams:chart];
    }
}

customDrawing .h

@interface customDrawing : UIView <ChartDelegate>{
    DataModel *chartData;
}
@property (nonatomic, retain) DataModel *chartData;
@end

customDrawing.m

@synthesize chartData;
-(void)getParams:(DataModel *)dataModel{
        chartData = dataModel;
}

事实证明，数据没有传递到我的自定义视图中的 ChartData 对象。帮助？

Answer 1

你缺少基础知识。我认为您不需要代表来完成这项任务，但我们开始吧。

协议就像一份合同。在您的FlipsideViewController 类中，您定义了协议，该协议本质上表明如果您符合此协议，则必须实现此方法。

如何遵守协议？

在 MainViewController 中，@interface 看起来像这样

@interface MainViewController : UIViewController <FlipsideViewControllerDelegate>

事实上，您将协议写在尖括号中意味着您承诺遵守协议，因此必须

 - (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;

在 MainViewController.m 中实现。

现在，当 MainNavigationController 将自身设置为委托 (controller.delegate = self;) 时，它会完成链接。这允许 FlipsideViewController 调用

[delegate flipsideViewControllerDidFinish:self];

Which 将调用 MainViewController 中定义的方法，该方法会关闭模态视图控制器。

您已经定义了第二个协议（您可以将该方法添加到第一个协议中，然后您不必采用两个协议），并且正如其他人指出的那样，您没有通过这样做来链接这些类

controller.delegate2 = self;

这不会解决您的问题。您仍然需要通过将 ChartDelegate 添加到声明中来遵守它。一旦你这样做了，你仍然无法脱离水面，因为方法不正确。

完整解决方案 - 不使用委托，因为这里并不真正需要它们

MainViewController.h

@interface MainViewController : UIViewController <FlipsideViewControllerDelegate>

- (IBAction)showInfo:(id)sender;

@end

MainViewController.m

@implementation MainViewController

- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller
{
    [self dismissModalViewControllerAnimated:YES];
}

- (IBAction)showInfo:(id)sender
{    
    FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:@"FlipsideView" bundle:nil];
    controller.delegate = self;

    /*
     * The labelText property is defined in the header for FlipsideViewController
     * In this case this is the easiest way to get data from this controller to
     * the controller we are about to display
     */
    controller.labelText = @"WHAT EVER YOU WANT TO SEND"; // <---- sending data

    controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
    [self presentModalViewController:controller animated:YES];

    [controller release];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

FlipsideViewController.h

@class FlipsideViewController;

@protocol FlipsideViewControllerDelegate
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
@end

@interface FlipsideViewController : UIViewController


/*
 * These properties have been added. The label is used for displaying the text
 * and needs to be hooked up in Interface builder
 *
 * The NSString is the property that is holding the data passed from MainViewController
 */
@property (nonatomic, retain) IBOutlet UILabel *testLabel;
@property (nonatomic, copy) NSString *labelText; from MainViewControlller

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

- (IBAction)done:(id)sender;

@end

FlipsideViewController.m

@implementation FlipsideViewController

@synthesize delegate = _delegate;

/*
 * We need to synthesise out properties so we get our getters and setters created
 */
@synthesize testLabel = _testLabel;
@synthesize labelText = _labelText;

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];

    /*
     * This is called once the view is set up and all connections have been made in 
     * interface builder. Therefore we can now set the text of our test label
     */
    self.testLabel.text = labelText;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

#pragma mark - Actions

- (IBAction)done:(id)sender
{
    [self.delegate flipsideViewControllerDidFinish:self];
}

- (void)dealloc
{
    /*
     * Memory management for the ivars we added
     */
    [_testLabel release];
    [_labelText release];
    [super dealloc];
}

@end

Answer 2

您有两个属性：delegate 和 delegate2。您正在为 delegate 分配一个值，但稍后调用 delegate2 上的方法。

Answer 3

您需要分配 delegate2 （您的 customDrawing 类）。您仅分配委托。