Cant get objects from JSON NSDictonary - ios

Question

When I convert the JSON into an NSDictionary then call ObjectForKey: I get the error: -[__NSCFArray objectForKey:]: unrecognized selector sent to instance 0xa9801d0
My code for converting:
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"];
This is the file:
{
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;
}
)
I need to be able to get any object from the JSON but I do not know why this exception is being thrown.

Answer 1

Do you see that lonely ) right at the end of the JSON output you've provided. If you look at the actual log from Xcode you're likely to see that there is a matching ( which you've forgotten to copy and paste into your question.
What you actually have is JSON object that is an array not a dictionary, so when you are trying to get values for keys, the compiler is telling you that the array doesn't respond to that message.
That should help you unpack your JSON object, you need to iterate through an array of dictionaries extracting the values you need.

Answer 2

I will complete #Abizem answer by adding a short piece of code because I see that you are a beginner (I don't have any problem with that) and I know that when you start programming or a new language, code snippets are really useful (doesn't meter that google is full of JSON parsing tutorials and SO is full of posts that are having your problem unrecognized selector when parsing.)
So whenever you have a JSON that starts with ( it means that the JSON is an array, if the JSON starts with a { then the JSON is a dictionary.
In order to get objects from a JSON array you will have to iterate over it. The objects contained by the JSON can be dictionaries or arrays.
So if you have only dictionaries into your array you should use:
for(NSDictionary *contentDictionary in yourJSONObject) {
//do stuffs with your dictionary
}
If you have only arrays into your JSON you should use:
for(NSArray *contentArray in yourJSONObject) {
//do stuffs with your dictionary
}
If you have both arrays and dictionaries in your JSON you should use:
for(id unknownType in yourJSONObject) {
if([unknownType isKindOfClass:[NSDictionary class]]) {
NSDictionary *dict = (NSDictionary*)unknownType;
}
else if ([unknownType isKindOfClass:[NSArray class]]{
NSArray *array = (NSArray *)unknownType;
}
}
If your JSON is a dictionary then you can use the NSDictionary methods to get the proper values:
[dictJSON objectForKey:#"myKey"];

Answer 3

The JSON is an array not a dictionary. Get the first element from the array before you access it as a dictionary.

Answer 4

Your object json is an NSArray which you're trying to access like a NSDictionary (objectForKey:)