Question

I’m iOS Beginner, and I have some troubles with coding.
By sending ASIHTTPRequest:

NSURL *url = [NSURL URLWithString:@"http://search.twitter.com/search.json?geocode=37.781157,-122.398720,25km"];

I receive data like this:

            {
        "created_at" = "Fri, 25 Jan 2013 17:48:29 +0000";
        "from_user" = "ZacHWallS_SBI";
        "from_user_id" = 252712138;
        "from_user_id_str" = 252712138;
        "from_user_name" = "ZACH WALLS";
        geo = "<null>";
        id = 294864332490162176;
        "id_str" = 294864332490162176;
        "in_reply_to_status_id" = 294861687004225537;
        "in_reply_to_status_id_str" = 294861687004225537;
        "iso_language_code" = en;
        location = "BAY AREA CALIFORNIA";
        metadata =             {
            "result_type" = recent;
        };
        "profile_image_url" = "http://a0.twimg.com/profile_images/3029389178/e3567459d147bc5d0a10f3c797b477aa_normal.png";
        "profile_image_url_https" = "https://si0.twimg.com/profile_images/3029389178/e3567459d147bc5d0a10f3c797b477aa_normal.png";
        source = "&lt;a href=&quot;http://twitter.com/#!/download/ipad&quot;&gt;Twitter for iPad&lt;/a&gt;";
        text = "@LilTioSBi yee ima slide through prolly";
        "to_user" = LilTioSBi;
        "to_user_id" = 35629694;
        "to_user_id_str" = 35629694;
        "to_user_name" = "Nevin Tio";
    },

Next I do this:

-(void) requestFinished: (ASIHTTPRequest *) request {
NSString *theJSON = [request responseString];
SBJsonParser *parser = [[SBJsonParser alloc] init];
NSMutableArray *jsonDictionary = [parser objectWithString:theJSON];
//NSLog(@"\n\n%@", jsonDictionary);  
NSMutableArray *userName = [userinfo objectForKey:@"from_user"];
NSLog(@"\n\n\n%@",userName);

I need to capture “from_user”.
Then run, and compiler says: [__NSArrayM objectForKey:]: unrecognized selector sent to instance 0x755bbc0…
How do it correctly?

Answer 1

So, I’ll be begin by clarifying something, which is that it’s actually the runtime that is giving you the “[__NSArrayM objectForKey:]: unrecognized selector sent to instance 0x755bbc0” error.

Let’s break it down:

__NSArrayM sounds suspiciously like NSArray (NSArray is technically something called a class cluster, meaning you won’t always see exactly NSArray in practice, just something that works like one).

-objectForKey: is a method on NSDictionary

So, we’re calling a method on an array that we think is a dictionary (calling a method = sending a message, or “selector” in ObjC parlance).

It seems like you’ve omitted some of your code, but if you just passed the value from something like:

[jsonDictionary objectForKey:@"results"]

You would end up with an array of tweets. You then need to grab an item from that array to get at its from_user key.

NSArray *tweets = [jsonDictionary objectForKey:@"results"];
NSDictionary *tweet = [tweets objectAtIndex:0];
NSString *username = [tweet objectForKey:@"from_user"];