将数据从一个 ViewController 发送到另一个。

Question

我有两个 ViewController：

1) 视图控制器

2) TestAppViewController

在ViewController.h 中，我定义了一个标签，我希望从第二个viewController 发送其文本，即`TestAppViewController。

为此，我在 ViewController.h 中定义了一个@property NSString *，并在我的第二个控制器中创建了这个 ViewController 的对象。 然后将一个值传递给该属性，但 ans 仍然为零。

以下是我的代码：

@property (nonatomic, retain) NSString *lableName;*

视图控制器

#import "ViewController.h
#import "TestAppView1.h"
#import "TestAppViewController2.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    //    [self addView1];
}

- (void)viewWillAppear:(BOOL)animated
{ 
    [self addView1];

    NSLog(@"Label name is %@",self.lableName);
}    

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

- (void)addView1
{
    TestAppView1 *testAppView1Obj = [ [TestAppView1 alloc]        initWithFrame:self.view.bounds];

    [testAppView1Obj setDelegate:self];
    [testAppView1Obj setSelectorOnButtonTapped:@selector(buttonTapped)];

    [self.view addSubview:testAppView1Obj];
}

 -(void)buttonTapped
 {

    TestAppViewController2 *testAppViewController2Obj =[[TestAppViewController2    alloc]initWithNibName:@"TestAppViewController2" bundle:nil];

    [self.navigationController pushViewController:testAppViewController2Obj animated:YES];
 }

 @end

ViewController2

#import "TestAppViewController2.h"
#import "TestAppView2.h"
#import "ViewController.h"

@interface TestAppViewController2 ()

@end

@implementation TestAppViewController2

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

-(void)viewWillAppear:(BOOL)animated
{
    [self addView2];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}



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

-(void)addView2
{
    TestAppView2 *testAppView2Obj =[ [TestAppView2 alloc]initWithFrame:self.view.bounds];

    [testAppView2Obj setDelegate:self];
    [testAppView2Obj setSelectorOnBackButton:@selector(callbackButtonTapped)];
    [self.view addSubview:testAppView2Obj];
}

-(void)callbackButtonTapped
{

    ViewController *viewControllerObj = [[ViewController alloc]init];

     viewControllerObj.lableName=@"Yogesh";    
     [self.navigationController popViewControllerAnimated:YES];


}

@end

当我尝试打印 NSLog 中的值时，它给了我 nil。

Answer 1

使用委托：

在 TestAppViewController.h 中：

   @protocol messageDelegate <NSObject>
    @optional
    -(void)test:(NSString*)str;
    @end
    @interface SecondViewController : NSString
    @property (nonatomic, assign) id <messageDelegate> delegate;
    @end

在 TestAppViewController.m 中：

-(void)readyToSend
{
    [self.delegate test:@"Hello world!"];

}

在 ViewController.h 中：

@interface ViewController : UIViewController<messageDelegate>
@end

在 ViewController.m 中：在

- (void)viewDidLoad {
TestAppViewController * testAppViewController = [[TestAppViewController alloc] init];
testAppViewController.delegate = self;
}
-(void) test:(NSString*)str{
NSLog(@"%@,str");
}

希望对您有所帮助！