将 JSON 解析为 UILabel 时出现空数组错误

Question

我正在尝试从我的服务器上的 JSON 文件中解析一些文本。我从文件中解析了三个不同的值："value1":"some_value"、"value2":"some_value"、"value3":"some_value"。

我声明了一个名为 statsHome 的 NSMutableArray，我在 viewDidLoad 方法中对其进行了初始化，如下所示：statsHome = [[NSMutableArray alloc] init];

问题是我初始化数组后，需要设置一个NSDictionary。如果我要在表格视图中这样做，我会写：

NSDictionary *stats = [self.statshome objectAtIndex:indexPath.row];

但我没有将这些值解析到表格视图中。我想将它们解析为 UILabel。所以我尝试的是声明新的NSUInteger。因为我不能在 viewDidLoad 方法中使用indexPath.row。我称它为statsIndex。

但是当我启动应用程序时它崩溃并给我这个错误消息：Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'

其余代码如下所示：

@interface DEMOHomeViewController () {
    NSUInteger statsIndex;
}
@end

@implementation DEMOHomeViewController
@synthesize statsHome;
@synthesize twitterFollowers;
@synthesize facebookLikes;
@synthesize instagramFollowers;

- (void)viewDidLoad
{
    [super viewDidLoad];  

    statsHome = [[NSMutableArray alloc] init];

    NSDictionary *stats = [self.statsHome objectAtIndex:statsIndex];

    value1.text = [stats objectForKey:@"value1"];
    value2.text = [stats objectForKey:@"value2"];
    value3.text = [stats objectForKey:@"value3"];

    NSURL *url1 = [[NSURL alloc] initWithString:@"the-json-file-with-the-values.php/file.json"];
    NSURLRequest *request1 = [[NSURLRequest alloc] initWithURL:url1];

    AFJSONRequestOperation *operation1 = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
        self.statsHome = [[NSArray alloc] initWithArray:JSON];
        [self.activityIndicatorView stopAnimating];

    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
        NSLog(@"Request Failed with Error: %@, %@", error, error.userInfo);
    }];

    [operation1 start];

}

@end

Answer 1

错误是正确的：您试图在设置数据之前从数组中获取数据。您应该在下面的代码中执行类似的操作。

- (void)viewDidLoad
{
    [super viewDidLoad];  

    NSURL *url1 = [[NSURL alloc] initWithString:@"the-json-file-with-the-values.php/file.json"];
    NSURLRequest *request1 = [[NSURLRequest alloc] initWithURL:url1];

    AFJSONRequestOperation *operation1 = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
        [self.activityIndicatorView stopAnimating];
        [self updateDataWithJSON:JSON]; // <- Here we will update our data
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
        NSLog(@"Request Failed with Error: %@, %@", error, error.userInfo);
    }];

    [operation1 start];

}

- (void)updateDataWithJSON:(id)JSON 
{
    self.statsHome = [[NSArray alloc] initWithArray:JSON];

    NSDictionary *stats = [self.statsHome objectAtIndex:statsIndex];

    value1.text = [stats objectForKey:@"value1"];
    value2.text = [stats objectForKey:@"value2"];
    value3.text = [stats objectForKey:@"value3"];
}

让我给你一个建议。似乎您的 statsIndex 在您的应用程序的其他部分初始化。在这种情况下，最好在每次访问此数组时检查 statsIndex 是否适合数组长度。否则在某些情况下可能是应用程序崩溃的原因：例如，您将数组放在其他控制器中，并且它有 10 个元素。您选择最后一个元素，但在 DEMOHomeViewController 的 viewDidLoad 中重新加载请求。而此时数组只有 9 个元素（最后一个元素已被其他人删除）。 -> 崩溃

Answer 2

NSURL *url = [NSURL URLWithString: [NSString stringWithFormat:@"url"];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

[request setHTTPMethod:@"GET"];

[request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];

NSString *authStr = [NSString stringWithFormat:@"%@:%@", @"usernmae", @"password"];

NSData *authData = [authStr dataUsingEncoding:NSUTF8StringEncoding];

NSString *authValue = [NSString stringWithFormat:@"Basic %@", [authData base64EncodedStringWithOptions:0]];

NSLog(@"%@",authValue);//

[request setValue:authValue forHTTPHeaderField:@"Authorization"];

[request setURL:url];
NSLog(@"%@",url);

NSError *error;

NSHTTPURLResponse *response;

NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

NSLog(@"Response code: %ld", (long)[response statusCode]);

NSLog(@"Data is %@",data);