A table view cell that displays a grid of months by conforming to ButtonGridDisplayable.

MonthGridCell.swift

//
//  MonthsOfYearGridCell.swift
//  Summit_iOS
//
//  Created by Ben Winters on 9/25/17.
//  Copyright © 2017 Goals LLC. All rights reserved.
//

import UIKit

protocol MonthsOfYearGridCellDelegate: class {
    
    func didSelectMonths(_ months: Set<Int>)
    
}

struct MonthsOfYearGridCellModel {
    
    var selectedMonths: [Int]
    weak var delegate: MonthsOfYearGridCellDelegate!
    
}

class MonthsOfYearGridCell: UITableViewCell {

    //This keeps the width constrained and centered on larger devices
    @IBOutlet weak var gridContainer: UIView!
    
    //All 3 of the outer stack views are vertical
    @IBOutlet weak var hSeparatorContainerStack: UIStackView!
    @IBOutlet weak var vSeparatorContainerStack: UIStackView!
    @IBOutlet weak var buttonContainerStack: UIStackView!
    
    private weak var delegate: MonthsOfYearGridCellDelegate!
    
    let separatorThickness = Style.separatorHeight
    let selectedColor = Style.primaryFillLight
    let separatorColor = Style.cellSeparator
    
    let buttonValues = Array(1...12)
    let columnCount = 4
    
    var selectedValues: Set<Int> = [] {
        didSet {
            didSetSelectedValues()
        }
    }
    
    static func newInstance(for tableView: UITableView, at indexPath: IndexPath, with cellModel: MonthsOfYearGridCellModel) -> MonthsOfYearGridCell {
        guard let cell = tableView.dequeueReusableCell(withIdentifier: .monthsOfYearGrid, for: indexPath) as? MonthsOfYearGridCell else { return MonthsOfYearGridCell() }
        cell.setup(with: cellModel)
        return cell
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
        
        setupStackViews()
        addSeparators()
    }
    
    func setup(with cellModel: MonthsOfYearGridCellModel) {
        self.applyStandardFormatting()
        self.delegate = cellModel.delegate
        
        setupButtons()
        self.selectedValues = Set(cellModel.selectedMonths) //didSet configures the selected buttons
    }
    
}

extension MonthsOfYearGridCell: ButtonGridDisplayable {
    
    @objc func didTapButton(sender: UIButton) {
        let month = sender.tag
        
        if selectedValues.contains(month), selectedValues.count != 1 {
            selectedValues.remove(month)
        } else {
            selectedValues.insert(month)
        }
        //didSet will change button.isSelected appropriately
        
        delegate.didSelectMonths(selectedValues)
    }
    
    func titleForButtonValue(_ value: Int) -> String? {
        return Date.mmmDescription(for: value)
    }
    
}