在 UIPickerview xcode 上解析 JSON 值

Question

我有一个pickerview，我想通过它使用JSON 解析来显示值。我知道网站上的一些问题已经解决了解析和pickerview，但我的json文件结构略有不同。这是 json 文件的示例。

[
{
"model":"juice",
"id" :
  [
    {
        "version": "version01"
    },

    {
        "version": "version02"
    }

  ]
},
 {
"model":"cream",
"id" :
[
  {
      "version": "cream01"
  },

  {
      "version": "cream02"
  }
]
}
]

还有我的 .m 文件

- (void)viewDidLoad
    {
    [super viewDidLoad];

    NSURL * serverhost = [NSURL URLWithString:@"http://my.json"];

    NSError *error;

    NSData  * Data  = [NSData  dataWithContentsOfURL: serverhost];

    self.modelsArray= [NSJSONSerialization JSONObjectWithData:Data   options:NSJSONReadingAllowFragments error:&error];

    NSLog(@"%@", modelsArray);
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 2;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView
numberOfRowsInComponent:(NSInteger)component
{
    if (component == departments)
        return [self.modelsArray count];
    return [self.versionsArray count];
}


#pragma mark Picker Delegate Methods
- (NSString *)pickerView:(UIPickerView *)pickerView
         titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    if (component == departments)
          return [[self.modelsArray    objectAtIndex:row]objectForKey:@"model"];
    return [[[self.versionsArray objectAtIndex:row]objectForKey:@"model"]objectForKey:@"version"];
}

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:    (NSInteger)component
{
    if (component == departments)
    {
        NSString * selectedRow = [[self.modelsArray objectAtIndex: row]    valueForKey:@"version"];
        NSArray * array = [sybreDepts objectForKey:selectedRow];
        self.
    }
}

@end

Basically when I select a model i.e juice or cream on the first column the second column should display its contents with key being 'versions' thus when juice is selected "version01" and "version02" should be displayed on the second column.

关于return [[[self.versionsArray objectAtIndex:row]objectForKey:@"model"]objectForKey:@"version"]; 行，我不相信它执行正确，因为我收到错误

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString objectForKey:]: unrecognized selector sent to instance 0xa18c450' . Any suggestions ? Thanks

Answer 1

如果您很好地缩进您的 JSON 数据并查看它：

[
    {
        "model": "juice",
        "id" : [
            {
                "version": "version01"
            }, 
            {
                "version": "version02"
            }
        ]
    },
    ....

然后您会看到它具有以下结构（从外部元素到内部元素）：

1. 一个数组
2. 具有两个键的对象/字典：model 和 version
3. 键 model 的字符串和键 id 的对象/字典
4. （仅适用于键 id）键 version 的字符串

所以如果你想访问第一个模型的第二个版本，你必须这样写：

NSArray* versionsArray = [[self.modelsArray objectAtIndex:modelRow] objectForKey:@"id"];
NSString* versionName = [[versionArray objectAtIndex: versionRow] objectForKey:@"version"];

在您的代码中，我看不到 self.versionArray 被赋值的位置。正如我在评论中指出的那样，以下行与 JSON 数据结构不匹配：

return [[[self.versionsArray objectAtIndex:row]objectForKey:@"model"]objectForKey:@"version"];

部分：

[[self.versionsArray objectAtIndex:row]objectForKey:@"model"]

将返回一个NSString 实例。如果您随后调用 objectForKey:@"version"，您将收到 unrecognized selector sent 错误。

更新：

更改后的代码可能如下所示：

.h 文件：

NSInteger modelRow;

.m 文件：

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 2;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    if (component == departments)
        return [self.modelsArray count];

    NSArray* versionsArray = [[self.modelsArray objectAtIndex:modelRow] objectForKey:@"id"];
    return [versionsArray  count];
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    if (component == departments)
          return [[self.modelsArray objectAtIndex:row]objectForKey:@"model"];

    NSArray* versionsArray = [[self.modelsArray objectAtIndex:modelRow] objectForKey:@"id"];
    return [[versionsArray objectAtIndex:row] objectForKey:@"version"];
}

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:    (NSInteger)component
{
    if (component == departments)
    {
        modelRow = row;
        [pickerView reloadComponent:1];
    }
}

@end