Swift - Decoding a Deeply Nested Dictionary - swift

Question

I am so close - but I am struggling with a very simple function to allow me to access a data point deeply nested in my JSON. The example I am using is on the Google directions API.
Sample JSON (from GMapsAPI):
{
"geocoded_waypoints" : [
{
"geocoder_status" : "OK",
"partial_match" : true,
"place_id" : "ChIJ960bMolw44kRQcGOlOZQ-r8",
"types" : [ "premise" ]
},
{
"geocoder_status" : "OK",
"partial_match" : true,
"place_id" : "EiMxMTggU2FsZW0gU3QsIEJvc3RvbiwgTUEgMDIxMTMsIFVTQSIaEhgKFAoSCSvDfDSJcOOJEbQanF0WxROfEHY",
"types" : [ "street_address" ]
}
],
"routes" : [
{
"bounds" : {
"northeast" : {
"lat" : 42.3647252,
"lng" : -71.0555085
},
"southwest" : {
"lat" : 42.3644965,
"lng" : -71.05552419999999
}
},
"copyrights" : "Map data ©2018 Google",
"legs" : [
{
"distance" : {
"text" : "82 ft",
"value" : 25
},
"duration" : {
"text" : "1 min",
"value" : 11
},
"end_address" : "118 Salem St, Boston, MA 02113, USA",
"end_location" : {
"lat" : 42.3647252,
"lng" : -71.0555085
},
"start_address" : "115 Salem St, Boston, MA 02113, USA",
"start_location" : {
"lat" : 42.3644965,
"lng" : -71.05552419999999
},
"steps" : [
{
"distance" : {
"text" : "82 ft",
"value" : 25
},
"duration" : {
"text" : "1 min",
"value" : 11
},
"end_location" : {
"lat" : 42.3647252,
"lng" : -71.0555085
},
"html_instructions" : "Head \u003cb\u003enorth\u003c/b\u003e on \u003cb\u003eSalem St\u003c/b\u003e toward \u003cb\u003eJerusalem Pl\u003c/b\u003e",
"polyline" : {
"points" : "ciqaG~_upLO?]A"
},
"start_location" : {
"lat" : 42.3644965,
"lng" : -71.05552419999999
},
"travel_mode" : "DRIVING"
}
],
"traffic_speed_entry" : [],
"via_waypoint" : []
}
],
"overview_polyline" : {
"points" : "ciqaG~_upLm#A"
},
"summary" : "Salem St",
"warnings" : [],
"waypoint_order" : []
}
],
"status" : "OK"
}
Decodable Structure: To work with this, I am using Decodable. I have been able to access first level nested data (routes.summary), but I am struggling to get further down (for example: routes.legs.duration). My code structure is as follows:
struct Directions: Decodable {
let status: String
let routes: [Routes]
enum CodingKeys :String, CodingKey {
case status, routes
}
struct Routes: Decodable {
let summary: String
let legs: [Legs]
enum CodingKeys : String, CodingKey {
case summary, legs
}
}
struct Legs: Decodable {
let duration: Duration
enum CodingKeys : String, CodingKey {
case duration
}
}
struct Duration: Decodable {
let text: String
enum CodingKeys : String, CodingKey {
case text
}
}
Implementation after URL set-up:
URLSession.shared.dataTask(with: url) { (data, response, err) in
guard let data = data else { return }
do {
let directions = try
JSONDecoder().decode(Directions.self, from: data)
for item in directions.routes {
self.stringoutput = item.summary
}
After all this, all I want to do is be able to access "text" in the JSON and return that value. The last line in the code is able to successfully return "summary" in the JSON; and I can print(directions) and the whole array/dictionary will return in the debug area, including "text". But I still can't figure out how to do:
x = directions.routes.legs.duration.text
to make x equal to "1 min"
Would be appreciative of anyone's help.
Edit: What ended up working is Vadian's struct keys below and the following for in loop:
for item in directions.routes {
print(item.summary)
self.direct = item.summary
for items in item.legs {
self.stringoutput = items.duration.text
print(items.duration.text)
}
Cheers!

Answer 1

These structs don't decode all keys, but it's a starting point.
If keys and struct members have the same name you don't need to specify CodingKeys
struct Directions: Decodable {
let status: String
let routes: [Route]
}
struct Route: Decodable {
let summary: String
let legs: [Leg]
}
struct Leg: Decodable {
let duration : TextValue
let distance : TextValue
let endAddress : String
let endLocation : Location
let startAddress : String
let startLocation : Location
let steps : [Step]
}
struct TextValue: Decodable {
let text: String
let value : Int
}
struct Location: Decodable {
let lat, lng : Double
}
struct Step: Decodable {
let duration : TextValue
let distance : TextValue
let endLocation : Location
let startLocation : Location
let htmlInstructions : String
let travelMode : String
}
To decode the snake_cased keys properly you have to add the appropriate key decoding strategy
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
To access the arrays ([]) you have to get an item by index
step[0]
or iterate the array with a loop
for step in steps {}