iOS构建视图以编程方式取决于对象ivar

Question

我有一个非常有趣的问题，涉及loadView,viewDidLoad,viewWillAppear和伊娃的状态。我有一个基于导航的应用程序。从我的第一层次看，我有一个表格列表，然后点击其中一个单元格，它会将我带到二级视图（细节视图）。当我点击一个单元格时，我还向被推入的视图控制器添加了一个“Office”对象（其中包含像streetAddress和boxAddress这样的字符串）。然后，我使用Office对象的内容填充详细视图，如[box setText:[self.office boxAddress]];（框是UILabel）。现在我想在这里实现的是，有时boxAddress的stringValue是空的，在这种情况下，我不想向UILabel添加空字符串，而是要将下一个UILabel向上移动（并取代boxAddress）。因此，我已经做了一个有条件检查，看看boxAddress是否为空，如果它应该设置为UILabel s与特定的坐标，如果它不是空的，它应该设置UILabel s与其他特定的坐标。

我知道你应该使用viewWillAppear如果你希望每次加载视图时运行代码。但由于某种原因，viewWillAppear似乎只在boxAddress字符串为空时才会运行。如果我点击一个空格为boxAddress的单元格，它将使用我点击的最后一个单元格的值为boxAddress，该单元格的空格为非空的boxAddress。

我会在这里粘贴我的代码，看看你是否可以给我一个指针，说明我在这里做错了什么。

// Implement loadView to create a view hierarchy programmatically, 
// without using a nib. 
- (void)loadView { 

    //allocate the view 
    self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; 

    //set the view's background color 
    self.view.backgroundColor = [UIColor whiteColor]; 
} 

- (void)viewDidLoad 
{ 

    //add the labels 
    name = [[UILabel alloc] initWithFrame:CGRectMake(10.0,10.0,320.0,20.0)]; 
    [name setBackgroundColor:[UIColor clearColor]]; 
    [name setTextColor:[UIColor blackColor]]; 

    street = [[UILabel alloc] initWithFrame:CGRectMake(10.0,30.0,320.0,20.0)]; 
    [street setBackgroundColor:[UIColor clearColor]]; 
    [street setTextColor:[UIColor blackColor]]; 

    //if no box address, move up the rest of the addresses 
    if ([[self.office boxAddress] length] == 0) { 

     zip = [[UILabel alloc] initWithFrame:CGRectMake(10.0,50.0,320.0,20.0)]; 
     [zip setBackgroundColor:[UIColor clearColor]]; 
     [zip setTextColor:[UIColor blackColor]]; 

     phone = [[UILabel alloc] initWithFrame:CGRectMake(10.0,70.0,320.0,20.0)]; 
     [phone setBackgroundColor:[UIColor clearColor]]; 
     [phone setTextColor:[UIColor blackColor]]; 

     fax = [[UILabel alloc] initWithFrame:CGRectMake(10.0,90.0,320.0,20.0)]; 
     [fax setBackgroundColor:[UIColor clearColor]]; 
     [fax setTextColor:[UIColor blackColor]]; 

     [self.view addSubview:name]; 
     [self.view addSubview:street]; 
     [self.view addSubview:zip]; 
     [self.view addSubview:phone]; 
     [self.view addSubview:fax]; 

    } else { 

     box = [[UILabel alloc] initWithFrame:CGRectMake(10.0,50.0,320.0,20.0)]; 
     [box setBackgroundColor:[UIColor clearColor]]; 
     [box setTextColor:[UIColor blackColor]]; 

     zip = [[UILabel alloc] initWithFrame:CGRectMake(10.0,70.0,320.0,20.0)]; 
     [zip setBackgroundColor:[UIColor clearColor]]; 
     [zip setTextColor:[UIColor blackColor]]; 

     phone = [[UILabel alloc] initWithFrame:CGRectMake(10.0,90.0,320.0,20.0)]; 
     [phone setBackgroundColor:[UIColor clearColor]]; 
     [phone setTextColor:[UIColor blackColor]]; 

     fax = [[UILabel alloc] initWithFrame:CGRectMake(10.0,110.0,320.0,20.0)]; 
     [fax setBackgroundColor:[UIColor clearColor]]; 
     [fax setTextColor:[UIColor blackColor]]; 

     [self.view addSubview:name]; 
     [self.view addSubview:street]; 
     [self.view addSubview:box]; 
     [self.view addSubview:zip]; 
     [self.view addSubview:phone]; 
     [self.view addSubview:fax]; 
    } 

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

// viewWillAppear method is run every time the view is loaded as opposite to the viewDidLoad method which only is run once 
// in this program DisclosureDetail view needs to be loaded for each detail view with different content each time 
- (void)viewWillAppear:(BOOL)animated { 

    NSLog(@"%@", [self.office boxAddress]); 

    [name setText:[self.office name]]; 
    [street setText:[self.office streetAddress]]; 
    if ([[self.office boxAddress] length] > 0) { 
     [box setText:[self.office boxAddress]]; 
    } 
    [zip setText:[NSString stringWithFormat:@"%@ %@", [self.office zipCode], [self.office city]]]; 
    [phone setText:[self.office phoneNo]]; 
    [fax setText:[self.office faxNo]]; 

    [super viewWillAppear:animated]; 
} 

Answer 1

if ([[self.office boxAddress] length] > 0) { 
    [box setText:[self.office boxAddress]]; 
} 

如果boxAddress的长度为0，那么box将继续包含任何文本你在它设定的最后一次视图中显示。

每次出现视图时，您都需要隐藏并显示box，而不仅仅是当视图加载时，因为视图可能已加载，然后用于显示多个不同的office s。