FUIFilterFormCollectionViewCell

@MainActor
open class FUIFilterFormCollectionViewCell : FUIInlineValidationDrawingCollectionViewCell<FUIFilterFormView>, FUIFormCell

A UICollectionViewCell subclass that allows a user to read or enter a set of values using a grid of buttons. This is commonly used for composing filters.

The developer should set the following properties on the cell in their implementation of the UICollectionViewDataSource cellForItem(at:) function:

• title: The title of the property.
• value: An array of the selected indexes in the control. Uses the same index as the valueOptions array.
• `valueOptions: A string array of titles for the buttons in the control

And an onChangeHandler:

• onChangeHandler: a handler closure, which is invoked on changes to the value

Optionally, the developer may provide:

• allowsMultipleSelection: Indicates whether multiple buttons may be selected simultaneously (true). If false, the control behaves in “radio” mode. The default is true.
• allowsEmptySelection: Indicates whether the control allows zero items to be selected (true). If false, then once a value has been selected by the developer or user, taps by the user on the last selected item will be ignored instead of deselecting the item. The default is true.
• isEditable: Indicates whether the cell’s value may be modified. The default is true.

The following is an example of usage in an application, UICollectionViewController:

 // optionally, create an array of value option to localized string mappings
  let buttonTitles: [[String: String]] = [["radius": "Distance"], ["price": "Price"], ["rating": "Ratings"], ["avail": "Availability"]]

 // Register FUIFilterFormCollectionViewCell in viewDidLoad() method in the controller.
 override func viewDidLoad() {
     super.viewDidLoad()
     self.collectionView.register(FUIFilterFormCollectionViewCell.self, forCellWithReuseIdentifier:
     FUIFilterFormCollectionViewCell.reuseIdentifier)
 }

 func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
     let cell = collectionView.dequeueReusableCell(withReuseIdentifier: FUIFilterFormCollectionViewCell.reuseIdentifier,
                                                   for: indexPath) as! FUIFilterFormCollectionViewCell

     cell.valueOptions = buttonTitles.flatMap { $0.map { $0.value }}
     cell.title = "Sort By"
     cell.value = [1]
     cell.allowsMultipleSelection = true
     cell.allowsEmptySelection = false

     // MARK:  implement onChangeHandler
     cell.onChangeHandler = { [weak self] newValue in
        self.applyFilter(forDimensions: newValue)      // here, the cell input is set to a filter function
     }

    return cell
 }

## Theming Supported style classes:

 fdlFUIFilterFormCollectionViewCell
 fdlFUIFilterFormCollectionViewCell_title
 fdlFUIFilterFormCollectionViewCell_item_contentView
 fdlFUIFilterFormCollectionViewCell_item_titleLabel
 fdlFUIFilterFormCollectionViewCell_item_contentView_selected
 fdlFUIFilterFormCollectionViewCell_item_titleLabel_selected