Question

我正在努力了解＆＃34;应该如何执行SegueWithIdentifier＆＃34;。在storyBoard中，我创建了三个场景＆＃34; scene1，scene2，scene3＆＃34;。 Scene1通过名为＆＃34; scene1To2＆＃34;的segue链接到scene2，scene2通过名为＆＃34; scene2To3＆＃34;的segue链接到scene3。和scene3通过名为＆＃34; scene3To1＆＃34;的segue链接到scene1。

如下面的代码所示，我打电话给＃34; shouldPerformSegueWithIdentifier＆＃34;如果segue的标识符为＆＃34; scene3To1＆＃34;则返回NO。

在运行时，我预计当我尝试通过＆＃34; scene3To1＆＃34;从scene3转换到scene1时，转换不会发生，但它通常会发生...所以＆＃34; shouldperformSegueWithIdentifier＆的目的是什么？＃34;

码：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

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

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

 - (IBAction)from1To2:(id)sender {
    NSLog(@"in 1st scene");

       [self performSegueWithIdentifier:@"scene1To2" sender:self];
  }

   - (IBAction)from2To3:(id)sender {
    NSLog(@"in 2nd scene");

    [self performSegueWithIdentifier:@"scene2To3" sender:self];
    }

   - (IBAction)from3To1:(id)sender {
   [self performSegueWithIdentifier:@"scene3To1" sender:self];


   NSLog(@"in 3rd scene");
  }


  -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
  {
    NSLog(@"prepareForSegue");

     if ([segue.identifier isEqualToString:@"scene1To2"])
      {
      NSLog(@"transiting from scene1To2");

     } else if ([segue.identifier isEqualToString:@"scene2To3"])
     {
     NSLog(@"transiting from scene2To3");

     } else if ([segue.identifier isEqualToString:@"scene3To1"])

    {
    NSLog(@"transition from scene 3 back to scene 1");
    }

    }

  -(BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier  
   sender:(id)sender
   {
   NSLog(@"shouldPerformSegueWithIdentifier");

   if ([identifier isEqualToString:@"scene3To1"])
   {
    return NO;
    }


  return YES;
   }

  @end

输出：

2017-06-06 16:02:07.301 UnwindSegue-1[699:19450] in 1st scene
2017-06-06 16:02:07.315 UnwindSegue-1[699:19450] prepareForSegue
2017-06-06 16:02:07.316 UnwindSegue-1[699:19450] transiting from  
scene1To2
2017-06-06 16:02:07.320 UnwindSegue-1[699:19450]    
shouldPerformSegueWithIdentifier
2017-06-06 16:02:08.245 UnwindSegue-1[699:19450] in 2nd scene

2017-06-06 16:02:08.260 UnwindSegue-1[699:19450] prepareForSegue
2017-06-06 16:02:08.260 UnwindSegue-1[699:19450] transiting from    
scene2To3

2017-06-06 16:02:08.265 UnwindSegue-1[699:19450]    
shouldPerformSegueWithIdentifier
2017-06-06 16:02:09.165 UnwindSegue-1[699:19450] prepareForSegue
2017-06-06 16:02:09.165 UnwindSegue-1[699:19450] transition from 
scene 3 back to scene 1
2017-06-06 16:02:09.167 UnwindSegue-1[699:19450] in 3rd scene
2017-06-06 16:02:09.167 UnwindSegue-1[699:19450] 
shouldPerformSegueWithIdentifier

*故事板**：

Answer 1

问题是您将Segue 连接添加到按钮，但也将IBAction连接到该按钮...并且在您的IBAction代码中，您是为同一个Segue手动调用performSegueWithIdentifier。

要创建要手动调用的Segue，而不是从按钮中按住Ctrl键拖动，请从Controller图标中按住Ctrl键拖动：

现在，您可以将该逻辑放在IBAction方法中，而不是使用shouldPerformSegueWithIdentifier来确定是否继续。

shouldperformSegueWithIdentifier无法正常工作

1 个答案: