当我将JSON转换为NSDictionary时，请调用ObjectForKey:我收到错误：-[__NSCFArray objectForKey:]: unrecognized selector sent to instance 0xa9801d0
我的转换代码：
NSError *error;
NSData *responseData = [NSData dataWithContentsOfURL:dataURL];
NSDictionary *json = [NSJSONSerialization
JSONObjectWithData:responseData
options:kNilOptions
error:&error];
NSLog(@"%@",json);
//The exeption is hilighted here:
NSArray *objects = [[json objectForKey:@"data"] objectForKey:@"children"];
这是文件：
{
data = {
after = "<null>";
before = "<null>";
children = (
{
data = {
"approved_by" = "<null>";
author = Jonovono;
"author_flair_css_class" = "<null>";
"author_flair_text" = "<null>";
"banned_by" = "<null>";
clicked = 0;
created = 1371955129;
"created_utc" = 1371926329;
distinguished = "<null>";
domain = "self.redditdev";
downs = 1;
edited = 0;
hidden = 0;
id = 1gv8g1;
"is_self" = 1;
likes = "<null>";
"link_flair_css_class" = "<null>";
"link_flair_text" = "<null>";
media = "<null>";
"media_embed" = {
};
name = "t3_1gv8g1";
"num_comments" = 2;
"num_reports" = "<null>";
"over_18" = 0;
permalink = "/r/redditdev/comments/1gv8g1/rate_limiting_on_commenting/";
saved = 0;
score = 4;
selftext = "Can't really find anyone else having this issue. I am using this ruby library for reddit api wrapper: https://github.com/paradox460/snoo\n\nIt seems when I comment only the first one goes through, and any others fail. It does not seem to return a message, but I am guessing it's because of the message that only comment so much in so much time. How can I get around that? Or is something else causing it? Thanks.";
"selftext_html" = "<!-- SC_OFF --><div class=\"md\"><p>Can&#39;t really find anyone else having this issue. I am using this ruby library for reddit api wrapper: <a href=\"https://github.com/paradox460/snoo\">https://github.com/paradox460/snoo</a></p>\n\n<p>It seems when I comment only the first one goes through, and any others fail. It does not seem to return a message, but I am guessing it&#39;s because of the message that only comment so much in so much time. How can I get around that? Or is something else causing it? Thanks.</p>\n</div><!-- SC_ON -->";
subreddit = redditdev;
"subreddit_id" = "t5_2qizd";
thumbnail = "";
title = "Rate limiting on commenting?";
ups = 5;
url = "http://www.reddit.com/r/redditdev/comments/1gv8g1/rate_limiting_on_commenting/";
};
kind = t3;
}
);
modhash = 6dviotq5igca155758e9e858f1d863870f1b5296d9d571d45d;
};
kind = Listing;
},
{
data = {
after = "<null>";
before = "<null>";
children = (
{
data = {
"approved_by" = "<null>";
author = pipeep;
"author_flair_css_class" = "<null>";
"author_flair_text" = "<null>";
"banned_by" = "<null>";
body = "New accounts are severely rate limited on comment speed to prevent spamming. Once you accumulate some karma, that goes down rather quickly. I've found that my bot with a few thousand karma is able to post a few times a minute at peek without any problems.\n\nThe API returns an error if you post too quickly (Probably `RATELIMIT` or `SUBREDDIT_RATELIMIT`; I don't remember). You can either drop those comments or put them in a queue and retry later, hoping that your queue doesn't get too long.";
"body_html" = "<div class=\"md\"><p>New accounts are severely rate limited on comment speed to prevent spamming. Once you accumulate some karma, that goes down rather quickly. I&#39;ve found that my bot with a few thousand karma is able to post a few times a minute at peek without any problems.</p>\n\n<p>The API returns an error if you post too quickly (Probably <code>RATELIMIT</code> or <code>SUBREDDIT_RATELIMIT</code>; I don&#39;t remember). You can either drop those comments or put them in a queue and retry later, hoping that your queue doesn&#39;t get too long.</p>\n</div>";
created = 1371970411;
"created_utc" = 1371941611;
distinguished = "<null>";
downs = 0;
edited = 0;
gilded = 0;
id = cao9eaf;
likes = "<null>";
"link_id" = "t3_1gv8g1";
name = "t1_cao9eaf";
"num_reports" = "<null>";
"parent_id" = "t3_1gv8g1";
replies = {
data = {
after = "<null>";
before = "<null>";
children = (
{
data = {
"approved_by" = "<null>";
author = Jonovono;
"author_flair_css_class" = "<null>";
"author_flair_text" = "<null>";
"banned_by" = "<null>";
body = "Alright, thanks. Good to know it goes down with karma. So karma is good for something.";
"body_html" = "<div class=\"md\"><p>Alright, thanks. Good to know it goes down with karma. So karma is good for something.</p>\n</div>";
created = 1372014449;
"created_utc" = 1371985649;
distinguished = "<null>";
downs = 0;
edited = 0;
gilded = 0;
id = caoivdj;
likes = "<null>";
"link_id" = "t3_1gv8g1";
name = "t1_caoivdj";
"num_reports" = "<null>";
"parent_id" = "t1_cao9eaf";
replies = "";
"score_hidden" = 0;
subreddit = redditdev;
"subreddit_id" = "t5_2qizd";
ups = 1;
};
kind = t1;
}
);
modhash = 6dviotq5igca155758e9e858f1d863870f1b5296d9d571d45d;
};
kind = Listing;
};
"score_hidden" = 0;
subreddit = redditdev;
"subreddit_id" = "t5_2qizd";
ups = 1;
};
kind = t1;
}
);
modhash = 6dviotq5igca155758e9e858f1d863870f1b5296d9d571d45d;
};
kind = Listing;
}
)
我需要能够从JSON获取任何对象，但我不知道为什么会抛出此异常。
答案 0 :(得分：3)
您是否在您提供的JSON输出结尾处看到了孤独的)。如果您查看来自Xcode的实际日志，您可能会发现有一个匹配的(您忘记复制并粘贴到您的问题中。
您实际拥有的是JSON对象，它是一个数组而不是字典，所以当您尝试获取键的值时，编译器会告诉您该数组不响应该消息。
这应该可以帮助你解压缩你的JSON对象，你需要遍历一个字典数组来提取你需要的值。
答案 1 :(得分：1)
我将通过添加一小段代码来完成@Abizem答案，因为我发现你是初学者（我没有任何问题）而且我知道当你开始编程或新语言时，代码片段非常有用（不会计算谷歌充满了JSON解析教程，并且在解析时SO充满了你的问题unrecognized selector。）
因此，只要你有一个以(开头的JSON，就意味着JSON是一个数组，如果JSON以{开头，那么JSON就是一个字典。
为了从JSON数组中获取对象，您必须迭代它。 JSON包含的对象可以是字典或数组。
因此，如果你的数组只有字典，你应该使用：
for(NSDictionary *contentDictionary in yourJSONObject) {
//do stuffs with your dictionary
}
如果您的JSON中只有数组，则应使用：
for(NSArray *contentArray in yourJSONObject) {
//do stuffs with your dictionary
}
如果您的JSON中同时包含数组和词典，则应使用：
for(id unknownType in yourJSONObject) {
if([unknownType isKindOfClass:[NSDictionary class]]) {
NSDictionary *dict = (NSDictionary*)unknownType;
}
else if ([unknownType isKindOfClass:[NSArray class]]{
NSArray *array = (NSArray *)unknownType;
}
}
如果您的JSON是字典，那么您可以使用NSDictionary方法获取正确的值：
[dictJSON objectForKey:@"myKey"];
答案 2 :(得分：0)
JSON是一个数组而不是字典。在将其作为字典访问之前，从数组中获取第一个元素。
答案 3 :(得分：0)
您的对象json是您尝试访问的NSArray，如NSDictionary（objectForKey:）