Combining multiple JSONs with id - json

Question

I'm trying to fetch data from a public API. However, all the data I need is accessible only by calling multiple URLs.
However, each JSON provided have a station_id and I'm trying to combine the data based on this value.
I am not sure which strategy I should use to "merge" the results (see code below)
I tried calling both URL at the same time.
Also tried to add the data from the second URL after calling the first URL.
first URL (https://api-core.bixi.com/gbfs/es/station_information.json)
{"last_updated":1565466677,
"ttl":10,
"data":
{"stations":
[
{"station_id":"25",
"external_id":"0b100854-08f3-11e7-a1cb-3863bb33a4e4",
"name":"de la Commune / Place Jacques-Cartier",
"short_name":"6026",
"lat":45.50761009451047,
"lon":-73.55183601379395,
"capacity":89,}]
// ...
Second URL (https://api-core.bixi.com/gbfs/en/station_status.json)
{"last_updated":1565466677,
"ttl":10,
"data":
{"stations":
[
{"station_id":"25",
"num_bikes_available": 39,
"num_docks_available":50,}]
// ...
Excepted Result (This is the structure I am looking for, not the final code)
{"last_updated":1565466677,
"ttl":10,
"data":
{"stations":
[
{"station_id":"25",
"external_id":"0b100854-08f3-11e7-a1cb-3863bb33a4e4",
"name":"de la Commune / Place Jacques-Cartier",
"short_name":"6026",
"lat":45.50761009451047,
"lon":-73.55183601379395,
"capacity":89,
"num_bikes_available": 39,
"num_docks_available":50}]
//...
Structure I tried to pass the data in
struct BixiApiDataModel: Codable {
let last_updated: Int
let ttl: Int
let data: Stations
}
struct Stations: Codable {
let stations: [Station]
}
struct Station: Codable {
let station_id: String
let num_bikes_available: Int
let num_docks_available: Int
let external_id: String
let name: String
let short_name: String
let lat: Float
let lon: Float
let capacity: Int
}
Calling the URL
class Webservice {
func loadBixiApiDataModel(url: URL, completion: #escaping ([Station]?) -> ()) {
URLSession.shared.dataTask(with: url) { data, response, error in
guard let data = data, error == nil else {
completion(nil)
return
}
let response = try? JSONDecoder().decode(BixiApiDataModel.self, from: data)
if let response = response {
DispatchQueue.main.async {
completion(response.data.stations)
}
}
}.resume()
}
}
I'm trying to display the combined information of a station. I assume the data I fetch after calling the first URL isn't stored when I call the second URL.
Should I call both APIs separately, store the data and then combine everything using the station_id value?
Or is it possible to call each APIs and append the data from the second URL based on the station_id?
Thanks in advance for your help.

Answer 1

I would do it like this
Handle each download separately
Keep the resulting data in separate structs
Merge them into a third struct and then use that third struct internally in the app
Handle each download separately
Download the station information first and store it in a dictionary with station_id as key and then download station status and use the same id to match the downloaded elements
Keep the resulting data in separate structs
Since the content of the downloaded data is quite different between the to API calls I would use two different structs for them, StationInformation and StationStatus. Looking at the type of data you might actually want to download status more often than information which seems to be more static so that is another reason to keep them separate.
Merge them into a third struct...
I would create a third struct that contains information from the two other structs, either as just two properties (shown below) or with properties that are extracted from the others
Here is an example of how the third struct could be implemented
struct Station {
let information: StationInformation
var status: StationStatus?
init(information: StationInformation) {
self.information = information
}
var id: String {
return information.stationId
}
mutating func merge(status: StationStatus) {
guard self.id == status.stationId else { return }
self.status = status
}
}
The download function could be modified to be generic to simplify the code. First the structs need to be modified
struct BixiApiDataModel<T: Decodable>: Decodable {
let data: Stations<T>
}
struct Stations<T: Decodable>: Decodable {
let stations: [T]
}
struct StationInformation: Codable {
let stationId: String
let externalId: String
//... rest of properties
}
struct StationStatus: Codable {
let stationId: String
let numBikesAvailable: Int
let numDocksAvailable: Int
}
then the function signature needs to be changed to
func loadBixiApiDataModel<T: Decodable>(url: URL, completion: #escaping ([T]?) -> ()) {
and the decoding needs to be changed (notice the improved error handling, never use try?)
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
do {
let response = try decoder.decode(BixiApiDataModel<T>.self, from: data)
completion(response.data.stations)
} catch {
print(error)
}
And a simplified example of calling the function (but without any merging)
var informationArray: [StationInformation] = []
var statusArray: [StationStatus] = []
if let url = URL(string: "https://api-core.bixi.com/gbfs/es/station_information.json") {
loadBixiApiDataModel(url: url, completion: {(arr: [StationInformation]?) in
if let arr = arr { informationArray = arr }
print(informationArray.count)
})
} else { print("Not a valid url")}
if let url = URL(string: "https://api-core.bixi.com/gbfs/en/station_status.json") {
loadBixiApiDataModel(url: url, completion: {(arr: [StationStatus]?) in
if let arr = arr { statusArray = arr }
print(statusArray.count)
})
} else { print("Not a valid url")}