在视图之间传递变量的最佳方式

Question

我对xcode非常陌生& Objective-C（来自PHP）我已经开始玩了，并且发现很难在视图之间传递变量，这是我迄今为止所拥有的：

Game_info.h

#import <UIKit/UIKit.h> 

@interface Game_Info : UIViewController { 
    IBOutlet UITextField *groupName; 
    IBOutlet UISegmentedControl *gameType; 

} 

@property (nonatomic,retain) IBOutlet UITextField *groupName; 


- (IBAction) GameTypePicker; 
- (IBAction) KeyboardHide; 
- (IBAction) BackBTN; 
- (IBAction) NextBTN; 

@end 

Game_Info.m

#import "I_Dare_YouViewController.h" 
#import "Game_Info.h" 
#import "Game_TDoR.h" 


    @implementation Game_Info 
    @synthesize groupName; 


// Next Button 
-(IBAction) NextBTN{ 
    if ([groupName.text length] == 0) { 
     // Alert 
     UIAlertView *alert = [[UIAlertView alloc] 
           initWithTitle:@"Group Name" 
           message:@"Please enter a group name" 
           delegate:self 
           cancelButtonTitle:@"OK" 
           otherButtonTitles:nil 
           ]; 
     [alert show]; 
     [alert release]; 
    }else if([groupName.text length] < 3){ 
     // Alert 
     UIAlertView *alert = [[UIAlertView alloc] 
           initWithTitle:@"Group Name" 
           message:@"Please enter a name longer than 3 characters" 
           delegate:self 
           cancelButtonTitle:@"OK" 
           otherButtonTitles:nil 
           ]; 
     [alert show]; 
     [alert release]; 
    }else{ 
     Game_TDoR *screen = [[Game_TDoR alloc] initWithNibName:nil bundle:nil]; 
     screen.modalTransitionStyle = UIModalTransitionStyleCrossDissolve; 
     [self presentModalViewController:screen animated:YES]; 
     [screen release]; 

     Game_TDoR *screen1 = [[Game_TDoR alloc] initWithNibName:nil bundle:nil]; 
     NSLog(@"Game_Info: %@",self.groupName.text); 
     screen1.groupNameText = self.groupName.text; 
     [self presentModalViewController:screen1 animated:YES]; 
     [screen1 release]; 

    } 
} 

然后在另一个视图/ .h/.m文件中，我正在尝试访问'groupName'属性。

Game_TDoR.m

#import "I_Dare_YouViewController.h" 
#import "Game_Info.h" 
#import "Game_TDoR.h" 
@implementation Game_TDoR 
@synthesize groupNameText,Testlbl; 


- (void)viewDidLoad 
{ 
    NSLog(@"Game_TDoR: %@",self.groupNameText); 
    NSString *msg = [[NSString alloc] initWithFormat:@"Hello, %@",[self.groupNameText capitalizedString]]; 
    [Testlbl setText:msg]; 
    [msg release]; 

    [super viewDidLoad]; 
    // Do any additional setup after loading the view from its nib. 
} 

那么什么，我试图做的是第一个视图页面（Game_info）有一个文本输入框和IM试图传递的一个标签上的另一个观点上页面（Game_TDoR）

这是在的NSLog出来（注意，第二页（Game_TDoR）出来首先在日志中。

2011-07-17 00:25:34.765 I Dare You[3941:207] Game_TDoR: (null) 
2011-07-17 00:25:34.774 I Dare You[3941:207] Game_Info: Name 

问题解决了：

下一步按钮我需要添加变量之前我搬到网页（而不是其他方式 - 傻noobish的事情...）

 Game_TDoR *screen1 = [[Game_TDoR alloc] initWithNibName:nil bundle:nil]; 
     NSLog(@"Game_Info: %@",self.groupName.text); 
     screen1.groupNameText = self.groupName.text; 
     [self presentModalViewController:screen1 animated:YES]; 
     [screen1 release]; 

     Game_TDoR *screen = [[Game_TDoR alloc] initWithNibName:nil bundle:nil]; 
     screen.modalTransitionStyle = UIModalTransitionStyleCrossDissolve; 
     [self presentModalViewController:screen animated:YES]; 
     [screen release]; 

Answer 1

如果您需要从Game_Info视图控制器到Game_TDoR视图控制器，它是由前模态呈现合格groupName.text的价值，你可以在Game_TDoR声明一个属性来保存的值：

1）声明NSString财产Game_TDoR @interface块：

@property (nonatomic,copy) NSString *groupNameText; 

（请记住，合成或实现在执行块存取方法）

2）在NextBTN动作，之后您初始化Game_TDoR例如，设置属性：Game_Info的

Game_TDoR *screen = [[Game_TDoR alloc] init...]; 
screen.groupNameText = self.groupName.text; 

Answer 2

仅仅包括头文件不会使变量可用。你只包括类的定义（类是PHP的什么@interface是Obj-C）你必须实例化Game_Info并通过Game_Info的实例访问变量。

Answer 3

组名是成员（伊娃）。它的默认可见性是@protected，所以Game_Info之外的任何类都无法访问它，除非它们来自Game_Info。要使groupName可访问，您可以创建一个公开它的属性，也可以将其设置为@public。这是如何完成的，在Xcode的大量文档中有记录。

但是，作为对象的ivar（实例变量）的groupName只有在实际上存在Game_Info的实例时才存在。我假设你的程序中有一些全局可访问的Game_Info实例，我们称它为globalGameInfo。现在，您可以访问使用

UITextField *gName = [globalGameInfo groupName]; 

Answer 4

借此它的组名中的.h文件中SecondViewController

NSString *strABC; 

进行以下功能SecondViewController.m

-(void)setString:(NSString *)strEntered{ 
    strABC=strEntered; 
} 

现在在第一视图控制器不喜欢这个：

SecondViewController.m *objSecond = [[SecondViewController.m] initwithNibName:@"secondView.xib" bundle:nil]; 

[objSecond setString:@"Comment Controller"]; 
[self.navigationController pushViewController:objSecond animated:YES]; 
[objSecond release]; 

现在，在secondViewController viewWillAppear Method中写下这个。

-(void)viewWillAppear:(BOOL)animated{ 
     lblUserInput.text = strABC; 
} 

请检查拼写错误，因为我手写这个。希望这个帮助。

如果你不使用navigationContoller，那么你可以做这样的事情。

SecondViewControler *objSecond = [[SecondViewController] initwithNibName:@"secondview.xib" bundle:nil]; 
[objSecond setUserInput:txtUserInput.text]; 
[objSecond viewWillAppear:YES]; 
[self.view addSubview:objSecond]; 
[objSecond release];