How to efficiently extract data from JSON dictionary - ios

Question

I have recently used the following code to extract the ID of a location from a Foursquare API call with:
NSDictionary* foursquareJson = [NSJSONSerialization JSONObjectWithData:secureData options:kNilOptions error:&error];
NSDictionary *venuesDict = foursquareJson[#"response"];
NSArray *venuesArray = venuesDict[#"venues"];
NSDictionary *venuesDict2 = venuesArray[0];
NSArray *categoriesDict = venuesDict2[#"categories"];
NSDictionary *idDict = categoriesDict[0];
NSLog(#"ID is %#",idDict[#"id"]);
with original foursquareJson being:
2015-03-30 17:16:40.700 Voyagic[2833:718563] {
meta = {
code = 200;
};
response = {
venues = (
{
categories = (
{
icon = {
prefix = "https://ss3.4sqi.net/img/categories_v2/building/conventioncenter_";
suffix = ".png";
};
id = 4bf58dd8d48988d1ff931735;
name = "Convention Center";
pluralName = "Convention Centers";
primary = 1;
shortName = "Convention Center";
}
);
contact = {
formattedPhone = "[phone]";
phone = "[phone]";
};
hereNow = {
count = 0;
groups = (
);
summary = "Nobody here";
};
id = 4b6599d4f964a520f8f52ae3;
location = {
address = "Broad Sanctuary";
cc = GB;
city = London;
country = "United Kingdom";
distance = 2167;
formattedAddress = (
"Broad Sanctuary",
London,
"Greater London",
"SW1P 3EE",
"United Kingdom"
);
lat = "51.49997800145596";
lng = "-0.1289014132864838";
postalCode = "SW1P 3EE";
state = "Greater London";
};
name = "Queen Elizabeth II Conference Centre";
referralId = "v-1427732200";
specials = {
count = 0;
items = (
);
};
stats = {
checkinsCount = 3657;
tipCount = 15;
usersCount = 2407;
};
verified = 0;
}
);
};
}
but there surely must be a better way of accessing the ID which I don't know about (instead of creating 4 dictionaries and 2 array, which seems somewhat excessive :/ ). Any help would be greatly appreciated :)

Answer 1

Ultimately, the data will need to be accessed through the lists of dictionaries and arrays somehow, it just depends on where you want that to happen. You could use or make a parser for the JSON but that will ultimately still need to map the JSON data similarly to what you are doing. A simple and shorter way of accessing the data would be to not create a new variable in every iteration. Although it really is not much different:
NSDictionary *foursquareJson = [NSJSONSerialization JSONObjectWithData:secureData options:kNilOptions error:&error];
NSDictionary *objectId = foursquareJson[#"response"][#"venues"][0][#"categories"][0][#"id"];
NSLog(#"ID is %#",objectId);
Because of the dialogue in the comments of this answer I figured I should probably include a bit more information about your concern with creating "4 dictionaries and 2 arrays". When you use the JSON Serializer to create native objects from the JSON (first line above) you are creating all of the arrays and dictionaries needed to fully represent and store the entire JSON. The difference in code samples between what you originally posted and what I provided is really not a significantly different. If you are concerned with creating too many dictionaries or arrays you should attempt to filter out the JSON prior to deserializing it into native objects.