nodes.n_array[index].x and nodes.n_array[index].y are not updating. Circles stay at starting points even when dragging.

import SwiftUI

struct ContentView: View {
    @StateObject var nodes = Nodes()

    var body: some View {

        ZStack {   
            ForEach(0..<nodes.n_array.count) { index in
                nodes.n_array[index].drawShape()
                    .gesture(DragGesture()
                        .onChanged { value in
                            nodes.n_array[index].x = value.translation.width
                            nodes.n_array[index].y = value.translation.height
                        }
                        .onEnded { value in

                        }
                    )
            }
        }
    }
}

import Foundation
import SwiftUI

class Node: ObservableObject, Decodable {
    enum CodingKeys: CodingKey {
        case id, x, y, text, red, green, blue, shape
    }

    public let id: Int
    @Published var x: Double
    @Published var y: Double
    public let text: String
    public var red: Double
    public var green: Double
    public var blue: Double
    public var shape: Int

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        id = try container.decode(Int.self, forKey: .id)
        x = try container.decode(Double.self, forKey: .x)
        y = try container.decode(Double.self, forKey: .y)
        text = try container.decode(String.self, forKey: .text)
        red = try container.decode(Double.self, forKey: .red)
        green = try container.decode(Double.self, forKey: .green)
        blue = try container.decode(Double.self, forKey: .blue)
        shape = try container.decode(Int.self, forKey: .shape)
    }
}

extension Node {
    func circle() -> some View {
        Circle()
            .fill(Color(red: red, green: green, blue: blue))
            .frame(width: 64, height: 64, alignment: .center)
            .position(x: x, y: y)
    }

    func square() -> some View {
        Rectangle()
            .fill(Color(red: red, green: green, blue: blue))
            .frame(width: 64, height: 64, alignment: .center)
            .position(x: x, y: y)
    }

    @ViewBuilder func drawShape() -> some View {
        switch shape{
        case 1: circle()
        case 2: square()
            default: Text("Failed")
        }
    }
}

Class with array of nodes:

import Foundation

class Nodes: ObservableObject {
   @Published var n_array = [Node]()

    init() {
        let url = Bundle.main.url(forResource: "nodes", withExtension: "json")!
        let data = try! Data(contentsOf: url)
        n_array = try! JSONDecoder().decode([Node].self, from: data)
    }
}

You Node object is a class, which is a reference type. SwiftUI prefers to work with value types.

This is an issue because changing the value of a property of a class object doesn't change the object, so SwiftUI can't observe the change. Changing a value type creates a whole new item and destroys the old one, so SwiftUI sees the change and can update the View accordingly.

You should rework your code so that Node is a struct. I would also suggest using an enum instead of an Int for Node.shape. And instead of ForEach(0..<nodes.n_array.count) you should make Node conform to Identifiable and then loop through nodes.n_array directly rather than by index.

Thank you so much man. I really appreciate your help.