无法在标签或文本字段中显示字符串

Question

作为iOS编程新手，我有一个非常简单的问题。

我有an iPhone app，它获取Facebook用户数据（ID，姓名，性别，城市）。

使用NSLog打印数据就好了：

id: 597287941
first_name: Alexander
last_name: Farber
gender: male
city: Bochum, Germany

但是我无法在我的UI中显示数据：

我尝试使用UITextField和UILabel。

我尝试过使用

[[self userId] setText:dict[@"id"]];

和

[_firstName setText:dict[@"first_name"]];

我已经连接了IBOutlets just fine（我认为）：

以下是我的DetailViewController.h：

#import <UIKit/UIKit.h>

@interface DetailViewController : UIViewController

@property (strong, nonatomic) NSDictionary *dict;

@property (weak, nonatomic) IBOutlet UILabel *userId;
@property (weak, nonatomic) IBOutlet UILabel *firstName;
@property (weak, nonatomic) IBOutlet UILabel *lastName;
@property (weak, nonatomic) IBOutlet UILabel *gender;
@property (weak, nonatomic) IBOutlet UILabel *city;

@end

DetailViewController.m中有问题的部分：

- (void)setDict:(NSDictionary *)dict
{
    NSLog(@"id: %@", dict[@"id"]);
    NSLog(@"first_name: %@", dict[@"first_name"]);
    NSLog(@"last_name: %@", dict[@"last_name"]);
    NSLog(@"gender: %@", dict[@"gender"]);
    NSLog(@"city: %@", dict[@"location"][@"name"]);

    [[self userId] setText:dict[@"id"]];
    [_firstName setText:dict[@"first_name"]];
    [_lastName setText:dict[@"last_name"]];
    [_gender setText:dict[@"gender"]];
    [_city setText:dict[@"location"][@"name"]];
}

Answer 1

您正在初始化标签之前更新视图。仍然可以在setDict方法中调用prepareForSegue来传递信息，但将setText调用移动到新视图控制器的viewDidLoad方法中。这将在视图初始化后更新标签。

Answer 2

上面的@DanielM是正确的，但这是他想说的。在segue上调用setDict方法。这没关系，但唯一的工作就是保持这些值直到准备好视图......

这是 DetailViewController的完整实现：

// DetailViewController.h
#import <UIKit/UIKit.h>

@interface DetailViewController : UIViewController

// this must save the values from Facebook until the VC is ready to use them
@property (strong, nonatomic) NSDictionary *dict;

@property (weak, nonatomic) IBOutlet UILabel *userId;
@property (weak, nonatomic) IBOutlet UILabel *firstName;
@property (weak, nonatomic) IBOutlet UILabel *lastName;
@property (weak, nonatomic) IBOutlet UILabel *gender;
@property (weak, nonatomic) IBOutlet UILabel *city;

@end


@implementation DetailViewController

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

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

// this is the key:  you cannot set the state of your views before they have
// been created.
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    [[self userId] setText:dict[@"id"]];
    [_firstName setText:dict[@"first_name"]];
    [_lastName setText:dict[@"last_name"]];
    [_gender setText:dict[@"gender"]];
    [_city setText:dict[@"location"][@"name"]];
}

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

/* don't implement this.  it's called too early to make a difference 
- (void)setDict:(NSDictionary *)dict
{
    NSLog(@"id: %@", dict[@"id"]);
    NSLog(@"first_name: %@", dict[@"first_name"]);
    NSLog(@"last_name: %@", dict[@"last_name"]);
    NSLog(@"gender: %@", dict[@"gender"]);
    NSLog(@"city: %@", dict[@"location"][@"name"]);

    NSString *avatar = [NSString stringWithFormat:kAvatar, dict[@"id"]];
    NSLog(@"avatar: %@", avatar);

    [[self userId] setText:dict[@"id"]];
    [_firstName setText:dict[@"first_name"]];
    [_lastName setText:dict[@"last_name"]];
    [_gender setText:dict[@"gender"]];
    [_city setText:dict[@"location"][@"name"]];
}
*/

@end

Answer 3

我认为setText已弃用SetText is Deprecated。我想你可以直接使用标签的文字属性。

firstName.text = dict[@"first_name"];

Answer 4

我认为编译器不知道它是什么类。您可以使用下面的示例进行显式演员测试吗？

- (void)setDict:(NSDictionary *)dict
{
    NSLog(@"id: %@", dict[@"id"]);
    NSLog(@"first_name: %@", dict[@"first_name"]);
    NSLog(@"last_name: %@", dict[@"last_name"]);
    NSLog(@"gender: %@", dict[@"gender"]);
    NSLog(@"city: %@", dict[@"location"][@"name"]);

    [[self userId] setText:dict[@"id"]];
    [_firstName setText:(NSString *)dict[@"first_name"]];
    [_lastName setText:(NSString *)dict[@"last_name"]];
    [_gender setText:(NSString *)dict[@"gender"]];
    [_city setText:(NSString *)dict[@"location"][@"name"]];
}