我对Objective-C和iOS编程还很陌生,在传递数据时遇到很多麻烦。我创建了一个模型“LevelsCompleted”,在其中声明了NSString属性:

@property (readwrite,copy) NSString *answersString;

我在.m文件中合成了它:
@synthesize answersString = _answersString;

现在,如果我在其中一个控制器中更改其值
-(void) changeAnswersString{
    LevelsCompleted *lvls = [[LevelsCompleted alloc] init];
    [lvls setAnswersString:@"1"];
}

然后从第三个控制器访问它:
-(void) showAnswerStringValue{
    LevelsCompleted *lvls = [[LevelsCompleted alloc]init];
    NSLog(@"%@", [lvls answersString]);
}

控制台显示null而不是1

我确实找不到为每个控制器更改数据的方法,而且我的英语非常有限,所以我不知道在文档中搜索什么。有什么帮助吗?

实际代码

// PuzzleOneViewController.m
#import "PuzzleOneViewController.h"
#import "LevelChooseViewController.h"

@interface PuzzleOneViewController(){
int thinInt;
int i;
int answer[10];
bool validSubmit, miniPresent, toDelete;
}
@end

@implementation PuzzleOneViewController

@synthesize levels;

- (IBAction)backButton:(id)sender {
if (levels ==nil) self.levels = [[LevelsCompleted alloc]init];
self.levels.answersString=@"Hello";
[self dismissModalViewControllerAnimated:NO];


}

@end

// PuzzleOneViewController.h
#import <UIKit/UIKit.h>
#import "LevelsCompleted.h"

@interface PuzzleOneViewController : UIViewController{
BOOL grosseur;
NSString *choice;
IBOutlet UIScrollView *sv;
IBOutlet UILabel *cluesLabel;
IBOutlet UILabel *hintLabelText;
   }

@property (nonatomic, retain) LevelsCompleted *levels;

- (IBAction)backButton:(id)sender;

@end

// LevelsCompleted.h这是我的模型
#import <Foundation/Foundation.h>

@interface LevelsCompleted : NSObject
{
int hello;
BOOL success[30];
NSString *answersString;
}
@property (readwrite,copy) NSString *answersString;

-(BOOL) success:(int)number;
-(void) setSuccess:(BOOL)result atIndex:(int)number;
@end

// LevelsCompleted.m
#import "LevelsCompleted.h"

@implementation LevelsCompleted
@synthesize answersString;

-(BOOL) success:(int)number{
    return success[number];
}
-(void) setSuccess:(BOOL)result atIndex:(int)number{
    success[number] = result;
}
@end

// LevelChooseViewController.m
#import "LevelChooseViewController.h"
#import "LevelsCompleted.h"
#import "PuzzleOneViewController.h"

@implementation LevelChooseViewController


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

-(void) viewWillAppear:(BOOL)animated{

PuzzleOneViewController *controller = [[PuzzleOneViewController alloc]init];

NSLog(@"%@",controller.levels.answersString);   // prints NULL
NSLog(@"%@", PuzzleOneViewController.levels.answersString); // Generates Error


}


-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if([[segue identifier] isEqualToString:@"PassLevelA"]){
    [[segue destinationViewController] setChoice:_levelChoice];

}
}

- (IBAction)Level1Choose:(id)sender {

_levelChoice = [[sender currentTitle]intValue];
[self performSegueWithIdentifier:@"PassLevelA" sender:self];
}
@end

在LevelChooseViewController.h文件中没有任何有趣的事情...
我无法复制所有内容,因为我的控制器每个都有500余行代码,但是我但是所有相关的内容(我希望如此...)非常感谢您的帮助

最佳答案

您没有访问相同的LevelsCompleted对象实例。 [[LevelsCompleted alloc] init]创建一个新的LevelsCompleted实例。这是与在changeAnswersString方法中创建的LevelsCompleted对象分离的对象。为了从“第三个控制器”访问完成级别的对象,您需要想出一种在两个控制器之间共享数据的方法。在不知道程序整体结构的情况下,很难确切地说出应该做什么,但是一个简单的选择是在第一个控制器或应用程序委托中添加一个“级别” @property,这样您就可以从其他地方:

在您的FirstController.h中:

@property (nonatomic, retain) LevelsCompleted *levels;

在您的FirstController.m中:
@synthesize levels;

然后,在changeAnswersString中:
- (void)changeAnswersString
{
    if (self.levels == nil) self.levels = [[LevelsCompleted alloc] init];
    self.levels.answersString = @"1";
}

现在,在showAnswerStringValue中:
- (void)showAnswerStringValue
{
    NSLog(@"%@", firstController.levels.answersString);
}

与往常一样,您应该仔细考虑程序的结构。不可能像这样一个简短的答案传达所有要考虑的事情,但是我建议您阅读标准的Cocoa设计模式,特别是模型视图控制器(MVC)范例。

关于objective-c - 如何从XCode 4.2中的不同 Controller 的模型更改数据,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/8694854/

10-12 01:37