_NSCFString allKeys，无法识别的选择器。我以为这是一个 NSDictionary ？

Question

我正在疯狂地试图弄清楚如何实现tableView numberofRowsinSection，并希望我能得到一些提示或建议。我觉得我把整个事情过于复杂化了。让我首先发布转换后的 xml 数据，该数据现在是 NSDictionary。

{
    "@body" = "";
    "@class_id" = "";
    "@title" = Discussions;
    "@type" = "Discussion Block";
},
{
    "@body" = "";
    "@class_id" = "";
    "@col" = 1;
    "@title" = YouTube;
    "@type" = "Youtube Block";
    item =     {
        "@body" = "http://www.youtube.com/watch?v=vDWhfsQHq1o&ob=av3e";
        "@title" = "Gavin DeGraw - Not Over You";
        "@type" = link;
    };
},
{
    "@body" = "";
    "@class_id" = "";
    "@title" = Calendar;
    "@type" = "Calendar Block";
},
{
    "@body" = "<p>  homework test</p> ";
    "@class_id" = "";
    "@title" = Homework;
    "@type" = "File Block";
    item =     (
                {
            "@body" = "https://MYDOMAIN.com/securelink;
            "@title" = "crashreport.rtf";
            "@type" = file;
        },
                {
            "@body" = "mydomain.com/securelink";
            "@title" = "Chem notes sep 26.docx";
            "@type" = file;
    }
);
},
{
    "@body" = "<p>  Link testing</p> ";
    "@class_id" = "";
    "@title" = Links;
    "@type" = "Link Block";
    item =     (
                {
            "@body" = "http://google.com";
            "@title" = Link1;
            "@type" = link;
        },
                {
            "@body" = "http://yahoo.com";
            "@title" = link2;
            "@type" = link;
        },
                {
            "@body" = "http://reddit.com";
            "@title" = link3;
            "@type" = link;
        }
    );
}
)

以上数据为响应。这样做的目标是使第一个标题键成为表标题，使第二个“标题”键（在“项目”内）成为各自部分的行。在 tableView TitleforHeaderinSection 方法中，我只需使用此代码

for (NSDictionary *roster in response) {
     [blockName addObject:[roster objectForKey@"@title"]];
 }
     return [blockName objectAtIndex:section];

numberofRowsinSection 方法是事情变得棘手的地方。这就是我尝试过的

for (NSDictionary *myDict in [[response objectAtIndex:section] valueForKeyPath:@"item"]) {
    NSArray *keys = [myDict allKeys];
    if ([keys containsObject:@"@title"]) {
        array3 = [[NSMutableArray alloc] init];
        [array3 addObject:[myDict objectForKey:@"@title"]];
    }
}
 return array3;

我得到的错误是 myDict 是 NSString 并且 allKeys 不能在其上使用。我不确定为什么会发生这种情况，因为当我将其更改为 objectAtIndex:1 并记录它时， allKeys 方法有效。我也很确定这不是查找每个部分所需行数的最佳方法，因此如果有更好的方法请分享。

只是为了澄清，这就是我在解析上述数据后在 tableView 中寻找的内容：

 Header (Discussions)
   -No rows under this header
 Header (YouTube)
   -Row (Gavin DeGraw - Not Over You)
 Header (Calendar)
   -No rows
 Header (Homework)
   -Row (crashreport)
   -Row (chem notes)
 Header (links)
   -Row (link1)
   -Row (link2)
   -Row (link3)

感谢您的帮助。我对 NSDictionary 和 NSArray 方法做了很多研究，但我不确定如何解决这个问题或以其他方式编码。

Answer 1

问题就在这里：

for (NSDictionary *myDict in [[响应 objectAtIndex:section]
valueForKeyPath:@"item"]) {

这对于下面的字典来说很好，因为它循环遍历 NSDictionary 对象的 NSArray。因此，当调用 [myDict allKeys] 时，您实际上是在 NSDictionary 上调用它。

{
    "@body" = "<p>  homework test</p> ";
    "@class_id" = "";
    "@title" = Homework;
    "@type" = "File Block";
    item =     (
                {
            "@body" = "https://MYDOMAIN.com/securelink;
            "@title" = "crashreport.rtf";
            "@type" = file;
        },
                {
            "@body" = "mydomain.com/securelink";
            "@title" = "Chem notes sep 26.docx";
            "@type" = file;
    }
);

但对于下一个字典来说并不好，因为您正在循环字典而不是数组，因此 for..in 循环正在循环字典的键。然后，您在 NSString（也称为字典中的键）上调用 allKeys。

{
    "@body" = "";
    "@class_id" = "";
    "@col" = 1;
    "@title" = YouTube;
    "@type" = "Youtube Block";
    item =     {
        "@body" = "http://www.youtube.com/watch?v=vDWhfsQHq1o&ob=av3e";
        "@title" = "Gavin DeGraw - Not Over You";
        "@type" = link;
    };
},

你可以这样做：

id item = [[response objectAtIndex:section] valueForKeyPath:@"item"];
if(item) {
    if([item isKindOfClass:[NSDictionary class]]) {
        NSArray *keys = [(NSDictionary *)item allKeys];
    } else if([item isKindOfClass:[NSArray class]]) {
        for (NSDictionary *myDict in (NSArray *)item) {
            NSArray *keys = [myDict allKeys];
        }
    }
}
else {
  return 0;
}

Answer 2

假设如果“item”键存在，那么对应的对象是一个 NSArray 的项目。

尝试：

NSArray *items = [[response objectAtIndex:section] valueForKey:@"item"];

if (items!=nil) {
    return [items count];
} else {
    return 0;
}