Grouping Json Data by Value in SwiftUI

Question

I'm new to SwiftUI and any help will be appreciated.

I have a Json file:

[
    {
        "id": 1001,
        "key1": "truck",
        "key2": "car1",
        "key3": "motorcycle",
    },
    {
        "id": 1002,
        "key1": "truck",
        "key2": "car2",
        "key3": "motorcycle",    
    },
    {
        "id": 1003,
        "key1": "truck",
        "key2": "car2",
        "key3": "motorcycle",    
    },
    {
        "id": 1004,
        "key1": "truck",
        "key2": "car2",
        "key3": "motorcycle",    
    },
    {
        "id": 1005,
        "key1": "truck",
        "key2": "car3",
        "key3": "motorcycle",    
    },
]

I can reach values like this:

VStack{    
    ForEach(userData.vehicles) { vehicle in
       Text(vehicle.key2)
           .foregroundColor(.white)
    }
}

The output is:

car1
car2
car2
car2
car3

What I want to see is:

car1
car2
car3

Is there any way to group the keys in SwiftUI?

Edit: @MahdiBM requested the following codes in comment section.

Vehicle declaration

final class UserData: ObservableObject {
    @Published var showFavoritesOnly = false
    @Published var vehicles = vehicleInfo
}

Reading Json

let vehicleInfo: [Vehicle] = readJSON("vehicleInfo.json")
func readJSON<T: Codable>(_ named: String) -> T {
    if let resPath = Bundle.main.resourcePath {
        do {
            let dirContents = try FileManager.default.contentsOfDirectory(atPath: resPath)
            let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
            let filteredFiles = dirContents.filter{ $0.contains(".json")}
            for fileName in filteredFiles {
                if let documentsURL = documentsURL {
                    let sourceURL = Bundle.main.bundleURL.appendingPathComponent(fileName)
                    let destURL = documentsURL.appendingPathComponent(fileName)
                    do {
                        try FileManager.default.copyItem(at: sourceURL, to: destURL)
                        print("Save to documents")
                    } catch {
                        print("ERROR FileManager.default.copyItem:: ", error)
                    }
                }
            }
        }catch { print("ERRIR 2", error) }
    }
    
    let data: Data
    do {
        let fileURL = try FileManager.default
            .url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
            .appendingPathComponent("vehicleInfo.json")
        
        data = try Data(contentsOf: fileURL)
        let foo = try JSONDecoder().decode(T.self, from: data)
//        print(foo)
        
        return foo
    } catch {
        fatalError("Couldn't find  in main bundle.")
    }
}

Edit 2:

struct Vehicle: Hashable, Codable, Identifiable {
    var id: Int
    var key1: String
    var key2: String
    var key3: String
}

SO says; "It looks like your post is mostly code; please add some more details."

They need to review this requirement I believe, because there is nothing I can say more.

How does vehicle declaration look like? How do you turn the json into vehicles? — Mahdi BM
– Mahdi BM, Commented Apr 11, 2021 at 13:44
thanks, i need to see Vehicle to be able to give you an appropriate answer. Something like struct Vehicle { var key1: String ...... }. This above code looks good though and at first glance doesn't have any real problems. — Mahdi BM
– Mahdi BM, Commented Apr 11, 2021 at 14:11
Thank you for trying to make my question clear. I also added that. — ilvthsgm
– ilvthsgm, Commented Apr 11, 2021 at 14:27
So you only want to access key2 from the struct? If not, in the json, do you consider all elements to be equal that has key2 = "Car2" even though the id is different for each? — Joakim Danielson
– Joakim Danielson, Commented Apr 11, 2021 at 14:42

Mahdi BM · Accepted Answer · 2021-04-11 14:43:07Z

1

Correct me if im wrong but from what i understand you have some Vehicles that can have a repetitive key2 and you don't like that. You instead want the key2s to not be repetitive.

var vehicles: [Vehicle] = [...]

// to group all `key2`s together, you can use `.map`:
var allKey2: [String] = vehicles.map { $0.key2 } // or `vehicles.map(\.key2)`, both are the same

// now you have all `key2`s grouped together
// to remove repetitive members, you can store the keys in a `Set` and convert them
// back to `Array`. why `Set`? because `Set` automatically removes repetitive members,
// but it also doesnt have any order for the members so we need to order the members back.
var noRepeatUnorderedAllKey2: [String] = Array(Set(allKey2))
// here we sort based on which member appeared sooner/later in the `allKey2` array
var noRepeatOrderedAllKey2: [String] = noRepeatUnorderedAllKey2.sorted {
    (allKey2.firstIndex(of: $0) ?? 0) < (allKey2.firstIndex(of: $1) ?? 0)
}

now you can do this, and you'll have car1, car2, car3 instead of car1, car2, car2, car2, car3:

VStack{    
    ForEach(noRepeatOrderedAllKey2) { vehicleKey2 in
       Text(vehicleKey2)
           .foregroundColor(.white)
    }
}

answered Apr 11, 2021 at 14:43

Mahdi BM

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3 Comments

ilvthsgm Over a year ago

You are right and thank you so much for your time. I got following error: Cannot use instance member 'vehicles' within property initializer; property initializers run before 'self' is available. I initialized like this: init() { vehicles = [] } What could be the problem?

Mahdi BM Over a year ago

i need more context, where did you type that init() { vehicles = [] }? the error says you need to first set a value for all things in the struct before using any values of the struct, but i can't see why its saying that here.

ilvthsgm Over a year ago

My previous comment was wrong, I solved with using id: \.self in ForEach. Your solution is top-notch, thank you so much for your help.

Joakim Danielson · Accepted Answer · 2021-04-11 16:02:21Z

1

I would introduce a new property in your UserData class to hold the unique keys from your Vehicle array. This property is automatically updated when the vehicles property is set.

final class UserData: ObservableObject {
    @Published var showFavoritesOnly = false
    @Published var vehicles: [Vehicle] {
        willSet {
            vehicleKeys = Set(newValue.map(\.key2)).sorted()
        }
    }
    @Published var vehicleKeys: [String] = []
}

And then you can use the vehicleKeys array in your ForEach and you could have a function that returns the Vehicle objects for the selected key.

Another option is to use a dictionary, since then you would have easier access to the corresponding Vehicle objects for a key

    @Published var vehicles: [Vehicle] {
        willSet {
            vehicleKeys = Dictionary(grouping: newValue, by: \.key2)
        }
    }
    @Published var vehicleKeys: [String: [Vehicle]] = [:]

Dictionaries aren't sorted though

edited Apr 11, 2021 at 16:02

answered Apr 11, 2021 at 15:26

Joakim Danielson

53.1k5 gold badges36 silver badges79 bronze badges

7 Comments

ilvthsgm Over a year ago

Thank you for your time. I got Class 'UserData' has no initializers error. How can I initialize it?

Joakim Danielson Over a year ago

init() { vehicles = [] } is one way.

ilvthsgm Over a year ago

I did like this: ForEach(userData.vehicleKeys, id: \.self) { vehicleKey in Text(vehicleKey)} No data show up. Do you know what could be the problem?

Joakim Danielson Over a year ago

Is userData declared with property wrapper @ObservedObject?

ilvthsgm Over a year ago

I use @EnvironmentObject var userData: UserData. I also tried @ObservedObject but some other view crashed with that. I believe @EnvironmentObject should work but no chance, no data show up.

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