Question

我对xcode＆amp; Objective-C（来自PHP）我已经开始玩了，发现很难在视图之间传递变量这是我到目前为止所做的：

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文件中我试图访问'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.
}

所以我想要做的是在第一个视图页面（Game_info）上有一个输入文本框，我试图将其传递给另一个视图页面上的标签（Game_TDoR）

这是NSLog中出现的内容（注意第二页（Game_TDoR）在日志中首先出现。

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：

在下一个按钮上我需要在移动页面之前添加变量（而不是相反 - 愚蠢的noobish要做的事情......）

        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

如果您需要将groupName.text的值从Game_Info视图控制器传递到前者以模态方式显示的Game_TDoR视图控制器，您可以在{中声明属性{1}}保存值：

1）在Game_TDoR @interface块中声明NSString属性：

Game_TDoR

（请记住在实现块中合成或实现访问器方法）

2）在@property (nonatomic,copy) NSString *groupNameText;操作中，初始化NextBTN实例后，设置属性：

Game_TDoR

Answer 2

仅包含头文件不会使变量可用。你只包括类的定义（类是用于PHP的@interface用于Obj-C）你必须实例化Game_Info并通过Game_Info实例访问变量。

Answer 3

groupName是Game_Info的成员（ivar）。它的默认可见性是@protected，因此Game_Info之外的任何类都无法访问它，除非它们派生自Game_Info。要使groupName可访问，您可以创建一个公开它的属性，也可以将其设为@public。如何做到这一点记录在Xcode的大量文档中。

但是，作为对象的ivar（实例变量）的groupName只有在实际存在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，我们称之为globalGameInfo。现在，您可以使用

访问其groupName

UITextField *gName = [globalGameInfo groupName];

Answer 4

在SecondViewController

中的.h文件中

NSString *strABC;

在SecondViewController.m

中创建以下函数

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

现在在第一个视图控制器中这样做：

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中，viewWillAppear方法写下这个。

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

我手写这个时请检查拼写错误。希望这有帮助。

如果您没有使用navigationContoller，那么您可以这样做。

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

在视图之间传递变量的最佳方法

4 个答案: