IP3S

Cell.swift

//
//  Cell.swift
//  marubatsu
//
//  Created by 29MCGD016 on 2021/11/26.
//

import SwiftUI

struct Cell: View {
    
    var boxState: Bool?
    var action: () -> ()
    
    var body: some View {
        Button(action: {
            self.action()
        }, label: {
            
            if let _boxState = boxState {
                Image(systemName: _boxState ? "circle" : "xmark")
            } else {
                // nil
                Text("s")
                    .foregroundColor(.white)
            }
        })
        
        .padding(20)
        .frame(width: 100, height: 100)
        .background(Color.white)
        .foregroundColor(boxState ?? true ? .red : .blue)
        
    }
}

struct Cell_Previews: PreviewProvider {
    static var previews: some View {
        Cell {}
    }
}

ContentView.swift

//
//  ContentView.swift
//  marubatsu
//
//  Created by 29MCGD016 on 2021/11/05.
//

import SwiftUI

struct ContentView: View {
    
    @State var boxList: [[Bool?]] = [
        [nil, nil, nil],
        [nil, nil, nil],
        [nil, nil, nil]
    ]
    
    var body: some View {
        
        VStack(spacing: 1) {
            ForEach(Array(zip(boxList.indices, boxList)), id: \.0) { (v, row) in // [Bool?]
                HStack(spacing: 1) {
                    ForEach(Array(zip(row.indices, row)), id: \.0) { (h, boxState) in
                        Cell(boxState: boxState) {
                            boxList[v][h] = !(boxState ?? false)
                        }
                    }
                }
            }
        }
        .background(Color.black)
        
        
        Button(action: {
//            if box1 == nil {
//                box1 = true
//            } else {
//                box1?.toggle()
//            }
            
        }, label: {
            
//            if let _box1 = box1 {
//                Image(systemName: _box1 ? "circle" : "xmark")
//            } else {
//                // nil
//                Text("a")
//            }
        })
        .background(Color.red)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}