NSDictionary annidate in swift - ios

Question

I have this json result.
I would take the field "alert".
I try this:
var alert: NSString = jsonResult["features"]["properties"]["alert"]
but this is the error: does not have a member named 'subscript'.
I can not how to access a field in a nested dictionary
{
features = (
{
geometry = {
coordinates = (
"-97.95359999999999",
"37.2382",
5
);
type = Point;
};
id = usb000si7g;
properties = {
alert = green;
cdi = "5.8";
code = b000si7g;
detail = "http://earthquake.usgs.gov/earthquakes/feed/v1.0/detail/usb000si7g.geojson";
dmin = "0.017";
felt = 1258;
gap = 38;
ids = ",usb000si7g,";
mag = "4.3";
magType = mwr;
mmi = "4.94";
net = us;
nst = "<null>";
place = "8km SE of Harper, Kansas";
rms = "0.51";
sig = 864;
sources = ",us,";
status = reviewed;
time = 1412272884590;
title = "M 4.3 - 8km SE of Harper, Kansas";
tsunami = "<null>";
type = earthquake;
types = ",cap,dyfi,general-link,geoserve,losspager,moment-tensor,nearby-cities,origin,phase-data,shakemap,tectonic-summary,";
tz = "-300";
updated = 1412614943519;
url = "http://earthquake.usgs.gov/earthquakes/eventpage/usb000si7g";
};
type = Feature;
}
);
metadata = {
api = "1.0.13";
count = 1;
generated = 1412617232000;
status = 200;
title = "USGS Significant Earthquakes, Past Week";
url = "http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/significant_week.geojson";
};
type = FeatureCollection;
}
I don't know what to do. swift is changed every beta.

Answer 1

As #Kirsteins said is his answer, you have to do a lot of unwrapping, and it's recommended to use a JSON library.
If you still want to stick with hand made extraction, then I suggest you to made it programmatically, such as adding an extension to NSDictionary as follows:
extension NSDictionary {
func objectForTreeKeys<T>(keys:[String]) -> T? {
var dict: NSDictionary? = self
var retValue: T?
for key in keys {
var value: AnyObject? = dict?.objectForKey(key)
if let unwrapped = value as? NSDictionary {
dict = unwrapped
} else if let unwrapped = value as? T {
retValue = unwrapped
break
} else {
retValue = nil
break
}
}
return retValue
}
}
You pass an array of keys to the function, and it traverses all nested dictionaries until:
a value of type T is encountered
a value having type different than NSDictionary and T is found
a nil value is found
In the first case, it returns the value of T type - in the other cases it returns nil.
You can use it as follows:
let ret: String? = jsonResult.objectForTreeKeys(["features", "properties", "alert"])
As you can see, it's a generic method, and the return type is inferred from the type of the variable the result is assigned to - so it's necessary to explicitly define its type, which must be optional (String? in this specific case).