Data Grid SwiftUI using LazyVGrid

DataGridView.swift

//
//  DataGridView.swift
//  Predictor
//
//  Created by Frank A. Krueger on 6/25/20.
//

import SwiftUI

struct Column: Identifiable {
    let id = UUID()
    var title: String
    var enabled: Bool = true
    var rows: [String] = (0..<512).map{x in "Row\(x)"}
}

struct DataGridView: View {
    var columns: [Column]
    
    let maxRows = 10000000
    
    struct CellIndex: Identifiable {
        let id: Int
        let colIndex: Int
        let rowIndex: Int
    }

    var body: some View {
        let numCols = columns.count
        let numRows = columns[0].rows.count
        let columnItems: [GridItem] = Array(repeating: .init(.flexible()), count: numCols)
        let cells = (0..<numRows).flatMap{j in columns.enumerated().map{(i,c) in CellIndex(id:j + i*maxRows, colIndex:i, rowIndex:j)}}
        return ScrollView {
            LazyVGrid(columns:columnItems) {
                ForEach(cells) { cellIndex in
                    let column = columns[cellIndex.colIndex]
                    HStack {
                        Spacer()
                        Text("\(column.title) \(cellIndex.rowIndex) \(column.rows[cellIndex.rowIndex])")
                        Spacer()
                    }
                }
            }
            .padding()
            .padding(.bottom, 44*4)
        }
    }
}

struct DataGridView_Previews: PreviewProvider {
    static var previews: some View {
        let cols = [
            Column(title: "A"),
            Column(title: "B"),
            Column(title: "C"),
            Column(title: "D"),
            Column(title: "E"),
            Column(title: "F"),
            Column(title: "G"),
            Column(title: "H"),
        ]
        return DataGridView(columns: cols)
    }
}