Parsing JSON with Objective-C

Question

For my project I have built my own api using PHP. The result of json encoding basically gives me an array of entries like below

{"terms":[
           {"term0":
               {"content":"test id",
                "userid":"100","translateto":null,
                "hastranslation":"0",
                "created":"2011-10-19 16:54:57",
                "updated":"2011-10-19 16:55:58"}
               },
           {"term1":
               {"content":"Initial content",
                "userid":"3","translateto":null,
                "hastranslation":"0",
                "created":"2011-10-19 16:51:33",
                "updated":"2011-10-19 16:51:33"
               }
           }
         ]
}

However, I've been having problems working with NSMutableDictionary and extracting "content" in Objective-C.

- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
[connection release];

NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
[responseData release];
NSMutableDictionary *JSONval = [responseString JSONValue];
[responseString release];

if (JSONval != nil) {
    NSMutableDictionary *responseDataDict = [JSONval objectForKey:@"terms"];
    if (responseDataDict!= nil) {
        for (id key in responseDataDict) {
            NSString *content = [[responseDataDict objectForKey:key]objectForKey:@"content"];
            [terms addObject:content];
            textView.text = [textView.text stringByAppendingFormat:@"\n%@", content];
        } 
        button.enabled = YES;
    }
}

}

Where NSLog spits out error when I send objectForKey to responseDataDict, which is a __NSArrayM according to the log.

What did I do wrong here?

Are you sure the JSON parser you’re using returns mutable collections? — user557219
– user557219, Commented Oct 20, 2011 at 6:49

user557219 · Accepted Answer · 2011-10-20 06:42:33Z

1

NSMutableDictionary *responseDataDict = [JSONval objectForKey:@"terms"];

But the value of "terms" isn’t a dictionary; it’s an array. Note the square brackets in your JSON string. You should use:

NSArray *terms = [JSONval objectForKey:@"terms"];

instead.

Note that each term in the array is an object (a dictionary) containing a single name (key) whose corresponding value (object) is, in turn, another object (dictionary). You should parse them as:

// JSONval is a dictionary containing a single key called 'terms'
NSArray *terms = [JSONval objectForKey:@"terms"];

// Each element in the array is a dictionary with a single key
// representing a term identifier
for (NSDictionary *termId in terms) {
    // Get the single dictionary in each termId dictionary
    NSArray *values = [termId allValues];

    // Make sure there's exactly one dictionary inside termId
    if ([values count] == 1) {
        // Get the single dictionary inside termId
        NSDictionary *term = [values objectAtIndex:0];

        NSString *content = [term objectForKey:@"content"]
        …
    }
}

Add further validation as needed.

answered Oct 20, 2011 at 6:42

user557219

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1 Comment

Simon Lee Over a year ago

That does the trick! I wasn't clear on how i should break down a JSON string, but your post is really helpful!! Thanks a lot!

Community · Accepted Answer · 2017-05-23 12:12:02Z

0

Refer this
How to Parse JSON in Cocoa/Objective-C.
How to parse JSON files on iPhone in Objective-C into NSArray and NSDictionary.
How to parse JSON into Objective C - SBJSON

edited May 23, 2017 at 12:12

CommunityBot

11 silver badge

answered Oct 20, 2011 at 6:28

Parag Bafna

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1 Comment

Marc Gravell Over a year ago

Answers that are just links are discouraged; it would be better to present a brief summary of how this applies

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