Parsing JSON into usable dictionaries - ios

Question

I'm currently building an food tracker iOS app (using swift 2) and I would like to have a database with all the foods (and their info) stored in the app and accessible.
The idea is that when some add a 'ice cream' to their meal, his calories/sugar/fat 'counters' increase by the respective nutritional value of the ice cream. (so that this data can be processed later on)
I have found a database of food in what seems like JSON format (see bellow) but I have no idea how to process all this data with swift so that I could access the number of calories in a specific ingredient for example.
So far I tried this:
let url = NSURL(string: "myURL")
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url!, completionHandler: { (data, response, error) -> Void in
if error != nil {
print(error)
} else {
let jsonResult = (try! NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers)) as! NSDictionary
print(jsonResult)
}
})
task.resume()
}
It allows me to process the JSON format into a dictionary that I can access but what I need (I think) would be maybe a dictionary of arrays and I can't manage to make it work with the JSON format that I have bellow.
[
{
"Description": "Juice",
"Energy(kcal)Per 100 g": 29,
},
{
"Description": "Alcoholic beverage, daiquiri, canned",
"Energy(kcal)Per 100 g": 125,
}
...
]
I admit my question wasn't quite clear at first (I'm really new at this I apologize) but I actually tried to research it on Stackoverflow before posting, but I haven't find something that works for my case. Sorry again and many thank you for taking the time to still answer it :)

Answer 1

Have a look into NSJSONSerialization. That is what you get for free once installed xcode and the SDK. And it is not that bad actually.
This is Ray's approach to Swifty Json:
http://www.raywenderlich.com/82706/working-with-json-in-swift-tutorial
This is what you find when you use the search. You will have to "translate" it to swift though.
How do I parse JSON with Objective-C?
You may want to look at RestKit for some more convenient way of dealing with JSON sources.
Give it a try. And when you run into concrete problems, then get back to SO.

Answer 2

Just give it a try
var arrDicts: [Dictionary<String, AnyObject>] = []
arrDicts = try! NSJSONSerialization.JSONObjectWithData(dataFromService!, options: NSJSONReadingOptions.AllowFragments) as! [Dictionary<String, AnyObject>]
dataFromService is the data that you have received from web service.

Answer 3

Answer for reference pruposes. How to do this in Objective-C
1- First get the info
a) If you are getting the JSON from an API or any online site:
//Set url of the JSON
NString *urlReq = #"http://www.URLHERE.com/PATH/TO/THE/JSON"
//Get data from the JSON
NSData *jsonData = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlReq]];
//Parse JSON
if(jsonData != nil){ //If the response is nil, the next line will crash
NSArray *resultArray = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:nil];
//Do stuff with the result...
}
b) If you are getting the information from the Core Data:
//Get context
NSManagedObjectContext *context = [self managedObjectContext];
//Preapre your fetch
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:#"Products" inManagedObjectContext:context];
NSFetchRequest *requestCoreData = [[NSFetchRequest alloc] init];
[requestCoreData setEntity:entityDescription];
//add predicates if needed
//Execute fetch
NSArray *resultArray = [context executeFetchRequest:requestCoreData error:nil];
//do stuff with the result....
2- Then parse the retrieved info
a) If you want a specific index:
NSString *description = resultArray[0][#"description"];
b) if you don't know what is the index you want (most likely what happens in your JSON):
BOOL found = NO;
int index = 0;
while(index < [resultArray count] && !found){
if([resultArray[index][#"description"] isEqualToString:#"Juice"])
found = YES;
else
++index;
}
if(found){
//'index' => index where the info you are searching can be found
}
else{
//The info couldn't be found in the array
}