Access Data Object by ID - swift

Question

I have the following structs that defined according to the SwiftUI example in Apple.
struct Cat: Hashable, Codable, Identifiable {
let id: Int
let name: String
let audio: [Int]? // list of audio of cat sound
}
struct CatAudio: Hashable, Codable, Identifiable {
let id: Int
let filename: String
}
I then would like to access the audio and then deliver in the view.
I have json data like this:
[
{
"id": 55,
"name": "meow",
"audio": [6,5]
},
{
"id": 3,
"name": "meowmeow",
"audio": [2]
}
]
AudioData.json
[
{
"id": 5,
"filename": "5.wav"
},
{
"id": 2,
"filename": "2.wav"
},
{
"id": 6,
"filename": "6.wav"
}
]
The json files loaded successfully.
#Published var cats: [Cat] = load("CatData.json")
#Published var catAudios: [CatAudio] = load("CatAudio.json")
I then tried to get an audio object from my environment model data:
#EnvironmentObject var modelData: ModelData
and then I want to get an the corresponding audio object of the cat. but I failed to do so as I do not know how to use the "Id" to get it.
Example:
Assume that I got the cat object from my model:
let cat = modelData.cats[0]
I then want to get its audio data according to the id stored in the audio list of it
let catAudio = modelData.catAudios[cat.audio[0]!] // exception here
I found that it is because the array order may not be consistent with the "Id". I want to make use of the "Id" instead of the Array order to get the item.
How can I do it?
========
I have tried to write a function to get the list of CatAudio of a cat.
I have also make audio non-optional.
func getAudio(cat: Cat) -> [CatAudio] {
return cat.audio.compactMap{id in catAudio.filter { $0.id==id } }
}
But it complains and said that cannot convert the value of type [CatAudio] to closure result type 'CatAudio'
I got confused with that.

Answer 1

You need to use high-order functions to match the id values in the audio array with the elements in the CatAudio array
Assuming the 2 arrays and a selected Cat object
var cats: [Cat] = ...
var catAudios: [CatAudio] = ...
let cat = cats[0]
To select one audio for a one id
if let firstId = cat.audio?.first {
let audio = catAudios.first { $0.id == firstId}
}
To get an array of all CatAudio for the cat object
if let array = cat.audio {
let values = array.compactMap { id in catAudios.filter { $0.id == id }}
}
The code would be simpler if the audio array wasn't optional, any reason for it to be declared optional?