Import JSON Array

Question

I am trying to import a JSON array and convert it to an NSArray for a UITableView, but can't work out how to grab the data.

My JSON is formatted as so when I use curl:

[{"location_name":"??"},{"location_name":"105"},{"location_name":"106"},{"location_name":"106A"},{"location_name":"106b"},{"location_name":"107"},{"location_name":"108"},{"location_name":"109"},{"location_name":"110"},{"location_name":"111"},{"location_name":"112"},{"location_name":"113"},{"location_name":"114"}]

My xCode code is as follows:

// Parse out the JSON data

NSError *jsonError;

NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&jsonError];

NSString* location_name = [json objectForKey:@"location_name"];

NSLog(@"Location Name: %@", location_name);

But in my console output I only get: "Location Name: (null)"

Have you tested the jsonError variable? That might give you some hints as to what is going on. — 67cherries
– 67cherries, Commented Feb 16, 2014 at 14:18
First, the JSON you have supplied is an array of objects, so using [json objectForKey:@"location_name"] will not produce anything. If you log out json what does it produce? — Nick
– Nick, Commented Feb 16, 2014 at 14:19
Are you sure you have given all the details here? The code you have should crash and not print Location Name: (null) — Paul.s
– Paul.s, Commented Feb 16, 2014 at 14:19
Go to json.org and spend the 5 minutes it takes to learn JSON syntax. What you have is an array of "objects" (dictionaries), not a single object/dictionary. And as @68cherries says, you should print the error parm, since it appears that the JSON did not convert at all. — Hot Licks
– Hot Licks, Commented Feb 16, 2014 at 14:27
Ok, wow, thanks, there are so many answers so quickly! I will work through, these make a lot of sense and I am sure they will fix it, thanks for your help, i'll report back with what works! — zipie
– zipie, Commented Feb 16, 2014 at 14:31

oli · Accepted Answer · 2014-02-16 14:24:42Z

2

Your root json object is not a dictionary but an array:

[{"location_name":"??"},{"location_name":"105"},{"location_name":"106"},{"location_name":"106A"},{"location_name":"106b"},{"location_name":"107"},{"location_name":"108"},{"location_name":"109"},{"location_name":"110"},{"location_name":"111"},{"location_name":"112"},{"location_name":"113"},{"location_name":"114"}]

As a result, here is how you can display its content:

NSError *e = nil;
NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableContainers error: &e];

if (!jsonArray) {
  NSLog(@"Error parsing JSON: %@", e);
} else {
   for(NSDictionary *item in jsonArray) {
      NSLog(@"Item: %@", item);
   }
}

answered Feb 16, 2014 at 14:24

oli

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2 Comments

zipie Over a year ago

Using this I am getting an error: "{NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}" I have tried allowing fragments but then get "{NSDebugDescription=Invalid value around character 0.}", Any ideas? Just googling up on it now.

zipie Over a year ago

*Its working! My PHP file had this line: print_r($result); Which must have been interfering, removed that and data is downloaded. Thanks so much!

tilo · Accepted Answer · 2014-02-16 14:18:26Z

1

Your JSON contains an array of dictionaries, thus do:

NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData:data 
                                                     options:NSJSONReadingMutableContainers 
                                                       error:&jsonError];

Then you can loop through the array (or pick the one according to the indexPath of your tableView) to get a single location.

answered Feb 16, 2014 at 14:18

tilo

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Comments

Florian Burel · Accepted Answer · 2014-02-16 14:23:47Z

0

You're json structure is an Array containing several object. When you parse it using the NSJSONSerialization, you get an NSArray back, not a NSDictionnary. So you probably need of a for loop!

NSError *jsonError;

NSArray *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&jsonError];

for(NSDictionnary * item in json)

{

NSString* location_name = [item objectForKey:@"location_name"];

NSLog(@"Location Name: %@", location_name);

}

answered Feb 16, 2014 at 14:23

Florian Burel

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Comments

Paul.s · Accepted Answer · 2014-02-16 14:24:04Z

0

If you literally just want to create an array of location_name's then you should change objectForKey: to valueForKey:, which will return you the array you want.

NSArray *locationNames = [json valueForKey:@"location_name"];

The reason this works is because you have an array of dictionaries. If you call valueForKey: on an array it will collect the result of calling valueForKey: on each of it's elements

answered Feb 16, 2014 at 14:24

Paul.s

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