调用 `reloadItems(at:)` 会导致程序崩溃

Question

我正在尝试创建一个程序，当用户在UITextField 中输入文本时，它会动态更新 collectoinView。下面是我为实现此目的而创建的扩展

我已根据您的建议更新了代码以包含插入和删除语句，我仍在重构和添加委托，但是虽然代码不会导致错误，但它不允许用户继续输入并关闭键盘我是否正确实现了所有内容

更新 #2（感谢您的所有帮助）

import UIKit

class ViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource, UICollectionViewDelegate, UISearchBarDelegate {

    lazy var collectionView : UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
        cv.backgroundColor = .white
        cv.delegate = self
        cv.dataSource = self
        return cv
    }()

    var genericTagsArray:[String] = ["tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za","tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za"]

    var currentTagsArray:[String] = [String]() {
        didSet {
            collectionView.reloadData()
        }
    }



    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.addSubview(collectionView)
        collectionView.register(Cell.self, forCellWithReuseIdentifier: "cell")
        collectionView.register(Header.self, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "header")
        collectionView.anchor(top: view.safeAreaLayoutGuide.topAnchor, leading: self.view.leadingAnchor, bottom: self.view.bottomAnchor, trailing: self.view.trailingAnchor, padding: .init(top: 30, left: 0, bottom: 30, right: 0))
        collectionView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0)


    }


    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return currentTagsArray.count
    }


    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! Cell
        cell.label.text = currentTagsArray[indexPath.item]
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        let header = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "header", for: indexPath) as! Header
        header.searchBar.delegate = self
        return header
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
        return CGSize(width: collectionView.contentSize.width, height: 75)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

        return CGSize(width: self.view.frame.size.width, height: 50)

    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 5
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 5
    }

    func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
        self.currentTagsArray = self.genericTagsArray.filter { (text) -> Bool in
            return text.contains(searchText.lowercased())
        }
    }
}

class Cell : UICollectionViewCell {

    let label = UILabel()

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupViews()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setupViews() {
        self.backgroundColor = .gray
        self.addSubview(label)
        label.anchor(top: self.topAnchor, leading: self.leadingAnchor, bottom: self.bottomAnchor, trailing: self.trailingAnchor)
    }

}

class Header: UICollectionReusableView{

    var searchBar = UISearchBar(frame: .zero)

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupViews()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setupViews() {
        self.backgroundColor = .gray
        self.addSubview(searchBar)
        searchBar.anchor(top: self.topAnchor, leading: self.leadingAnchor, bottom: nil, trailing: self.trailingAnchor, padding: .init(top: 0, left: 5, bottom: 0, right: 5), size: .init(width: 0, height: 50))
    }
}

extension UIView {
    func anchor(top: NSLayoutYAxisAnchor?, leading: NSLayoutXAxisAnchor?, bottom: NSLayoutYAxisAnchor?, trailing: NSLayoutXAxisAnchor?, padding: UIEdgeInsets = .zero, size: CGSize = .zero) {
        translatesAutoresizingMaskIntoConstraints = false

        if let top = top {
            topAnchor.constraint(equalTo: top, constant: padding.top).isActive = true
        }

        if let leading = leading {
            leadingAnchor.constraint(equalTo: leading, constant: padding.left).isActive = true
        }

        if let bottom = bottom {
            bottomAnchor.constraint(equalTo: bottom, constant: -padding.bottom).isActive = true
        }

        if let trailing = trailing {
            trailingAnchor.constraint(equalTo: trailing, constant: -padding.right).isActive = true
        }

        if size.width != 0 {
            widthAnchor.constraint(equalToConstant: size.width).isActive = true
        }

        if size.height != 0 {
            heightAnchor.constraint(equalToConstant: size.height).isActive = true
        }
    }
}

通过编辑更新函数

    @objc func textFieldDidChange(){
        guard(!(feedSearchBar.text?.isEmpty)!) else{
            VC.currentTagsArray = VC.genericTagsArray
            VC.feedScreenCollectionView.reloadData()
            return
        }
        VC.currentTagsArray = VC.genericTagsArray.filter({letter -> Bool in
            if feedSearchBar.text!.count > letter.count{
                return false
            }
            let stringRange = letter.index(letter.startIndex, offsetBy: feedSearchBar.text!.count)
            let subword = letter[..<stringRange]
            return subword.lowercased().contains(feedSearchBar.text!.lowercased())
        })

        if VC.currentTagsArray.isEmpty{
            VC.feedScreenCollectionView.deleteItems()
            VC.currentTagsArray.insert(feedSearchBar.text!, at: 0)           
            VC.feedScreenCollectionView.insertItems(at: [IndexPath(item: 0, section: 0)])
            //VC.feedScreenCollectionView.reloadItems(inSection: 0)           
           // VC.feedScreenCollectionView.reloadItems(at: [IndexPath(item: 0, section: 0)])
        }
      //VC.feedScreenCollectionView.reloadData()
     VC.feedScreenCollectionView.reloadItems(inSection: 0)
   }

extension UICollectionView{
    func reloadItems(inSection section:Int = 0) {
        var indicies:[IndexPath] = [IndexPath]()
        print("current number of items to reload \(self.numberOfItems(inSection: section))")
        for i in 0..<self.numberOfItems(inSection: section){
        indicies.append(IndexPath(item: i, section: section))
            print("current item number: \(i)")
        }
        self.reloadItems(at: indicies)
       // self.insertItems(at: indicies)
    }

    func deleteItems(inSection section:Int = 0){
        var indicies:[IndexPath] = [IndexPath]()
        for i in 0..<self.numberOfItems(inSection: section){
            indicies.append(IndexPath(item: i, section: section))
        }
        self.deleteItems(at: indicies)
    }
}

原始功能：

extension UICollectionView{
        func reloadItems(inSection section:Int = 0) {
            var indicies:[IndexPath] = [IndexPath]()
            for i in 0..<self.numberOfItems(inSection: section){
            indicies.append(IndexPath(item: i, section: section))
            }
            self.reloadItems(at: indicies)
        }
    }

但是，当我在编辑 textField 后调用此函数时，程序会因错误而崩溃

* -[UICollectionView _endItemAnimationsWithInvalidationContext:tentativelyForReordering:animator:] 中的断言失败，/BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3698.54.4/UICollectionView.m:5867 2018-07-18 16:28:02.226606-0400 FeedScreenReuseableView[87752:9704142] * 由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因：“尝试将第 6 项插入第 0 部分，但只有 6 个更新后第0节中的项目'

我不确定如何解决这个问题。有没有更好的方法来重新加载不影响标题的单元格。提前感谢您的所有帮助。以下是该项目的完整代码。

import UIKit

class ViewController: UIViewController,UICollectionViewDelegateFlowLayout,UICollectionViewDelegate,UICollectionViewDataSource,printDelegateWorkedDelegate,updateCollectionView{

    func updateCollectionView() {
        self.feedScreenCollectionView.reloadData()
    }

    func printDelegateWorkedDelegate() {
        print("The delegate worked")
    }

    var genericTagsArray:[String] = ["tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za","tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za"]
    var currentTagsArray:[String] = [String]()
    var tagsSelected:[String] = [String]()
    let keyboardSlider = KeyboardSlider()

    var header:feedViewHeader = feedViewHeader()

    @IBOutlet weak var feedScreenCollectionView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        keyboardSlider.subscribeToKeyboardNotifications(view: view)
        currentTagsArray = genericTagsArray

        let viewTapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(feedViewHeader.viewTapped(gestureRecognizer:)))
        viewTapGestureRecognizer.cancelsTouchesInView = false
        self.feedScreenCollectionView.addGestureRecognizer(viewTapGestureRecognizer)

        feedScreenCollectionView.delegate = self
        //
        feedScreenCollectionView.dataSource = self
        //

        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 5, left: 1, bottom: 0, right: 1)
        layout.minimumLineSpacing = 0
        layout.headerReferenceSize = CGSize(width: 50, height: 75)

        layout.sectionHeadersPinToVisibleBounds = true
        feedScreenCollectionView.collectionViewLayout = layout
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
            return CGSize(width: 50, height: 75)
    }
    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
                header = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "feedViewHeader", for: indexPath) as! feedViewHeader
            header.VC = self
        return header

    }
    //


    //Data Source
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return currentTagsArray.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "feedViewCell", for: indexPath) as! feedViewCell
        cell.feedImageView.backgroundColor = .blue
        cell.feedImageView.clipsToBounds = true
        cell.feedImageView.layer.cornerRadius = CGFloat((cell.feedImageView.frame.width)/5)
        cell.feedLabel.text = currentTagsArray[indexPath.item]
        return cell
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat{
        return 0
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let collectionViewWidth = collectionView.bounds.width/4.0
        let collectionViewHeight = collectionViewWidth
        return CGSize(width: collectionViewWidth-4, height: collectionViewHeight+25)
    }
    var lastContentOffset:CGFloat = 0

    func scrollViewDidScroll(_ scrollView: UIScrollView) {

        if self.lastContentOffset > self.feedScreenCollectionView.contentOffset.y && self.feedScreenCollectionView.contentOffset.y > 0 && self.feedScreenCollectionView.contentOffset.y < self.feedScreenCollectionView.frame.maxY {
            self.lastContentOffset = scrollView.contentOffset.y
            header.isHidden = false
        }
        else if (self.lastContentOffset < self.feedScreenCollectionView.contentOffset.y) && (self.feedScreenCollectionView.contentOffset.y < self.feedScreenCollectionView.frame.maxY) && (self.feedScreenCollectionView.contentOffset.y > 0)  {
            print("you scrolled down,content offSet: \(scrollView.contentOffset.y)->\(self.feedScreenCollectionView.contentOffset.y)")
            header.isHidden = true
        }
        else{
            self.lastContentOffset = scrollView.contentOffset.y
            print("content offSet: \(scrollView.contentOffset.y)")
            print("Nothing happened")
            //  self.headerDelegate?.hideHeaderView(hide: true)
        }


    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardFrameChangeNotification(notification:)), name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
    }

    var offsetY:CGFloat = 0

    @objc func keyboardFrameChangeNotification(notification: Notification) {
    }


}


class feedViewCell:UICollectionViewCell{

    @IBOutlet weak var feedImageView: UIImageView!
    @IBOutlet weak var feedLabel: UILabel!

    let keyboardSlider = KeyboardSlider()

    override func awakeFromNib() {
        super.awakeFromNib()
        feedLabel.translatesAutoresizingMaskIntoConstraints = false
        feedImageView.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
        feedImageView.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
        feedImageView.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
        feedImageView.bottomAnchor.constraint(equalTo: self.feedLabel.topAnchor).isActive = true

        feedImageView.translatesAutoresizingMaskIntoConstraints = false
        feedLabel.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
        feedLabel.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
        feedLabel.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
        feedLabel.topAnchor.constraint(equalTo: self.feedImageView.bottomAnchor).isActive = true
        feedLabel.textAlignment = .center

    }

}




class feedViewHeader:UICollectionReusableView,UITextFieldDelegate,UICollectionViewDelegate{

    @IBOutlet weak var feedSearchBar: UITextField!

    var delegateWorked:printDelegateWorkedDelegate?
    var updateCV:updateCollectionView?


    var VC:ViewController!
    var collectionView:UICollectionView?
    var stringToBeSet = "String to be set"

    override func awakeFromNib() {
        super.awakeFromNib()

        feedSearchBar.delegate = self
        feedSearchBar.autocorrectionType = .no
        feedSearchBar.keyboardType = .default
          feedSearchBar.addTarget(self, action: #selector(feedViewHeader.textFieldDidChange), for: .editingChanged)
        self.feedSearchBar.borderStyle = .roundedRect
        self.feedSearchBar.layer.borderColor = UIColor.black.cgColor
        self.feedSearchBar.layer.borderWidth = 4
        var searchBarHeight = self.feedSearchBar.bounds.height
        self.feedSearchBar.placeholder = "Tap To Search"
        self.feedSearchBar.returnKeyType = .search
        self.feedSearchBar.rightViewMode = .always
    }


    @objc func viewTapped(gestureRecognizer:UIGestureRecognizer){

        if  feedSearchBar.isFirstResponder{
            feedSearchBar.resignFirstResponder()
        }
    }

   func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
     VC.feedScreenCollectionView.reloadData()

    //VC.feedScreenCollectionView.reloadSections([0])
    return true
    }

    /// Helper to dismiss keyboard
    @objc func didStopEditing() {
    }

    func textFieldDidEndEditing(_ textField: UITextField) {
        UIView.setAnimationCurve(UIViewAnimationCurve.easeInOut)
        UIView.animate(withDuration: 0.2) {
            self.VC.view.frame.origin.y = 0
        }
    }
    @objc func textFieldDidChange(){
        guard(!(feedSearchBar.text?.isEmpty)!) else{
            VC.currentTagsArray = VC.genericTagsArray
            VC.feedScreenCollectionView.reloadData()
            return
        }

        VC.currentTagsArray = VC.genericTagsArray.filter({letter -> Bool in
           if feedSearchBar.text!.count > letter.count{
                return false
            }
            let stringRange = letter.index(letter.startIndex, offsetBy: feedSearchBar.text!.count)
            let subword = letter[..<stringRange]
            return subword.lowercased().contains(feedSearchBar.text!.lowercased())

        })

        if VC.currentTagsArray.isEmpty{
            VC.currentTagsArray.insert(feedSearchBar.text!, at: 0)
        }
    VC.feedScreenCollectionView.reloadItems(inSection: 0)
   }
}

extension Notification.Name{
    static let showKeyboard = Notification.Name("showKeyboard")
}
class KeyboardSlider: NSObject {
    // variables to hold and process information from the view using this class
    weak var view: UIView?

    @objc func keyboardWillShow(notification: NSNotification) {
        // method to move keyboard up
        // view?.frame.origin.y = 0 - getKeyboardHeight(notification as Notification)
        print("made it to keyboard will show")
    }

    func getKeyboardHeight(_ notification:Notification) -> CGFloat {
        // get exact height of keyboard on all devices and convert to float value to return for use
        let userInfo = notification.userInfo
        let keyboardSize = userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue
        return keyboardSize.cgRectValue.height
    }

    func subscribeToKeyboardNotifications(view: UIView) {
        // assigning view to class' counterpart
        self.view = view
        // when UIKeyboardWillShow do keyboardWillShow function
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil)
    }

    func unsubscribeFromKeyboardNotifications() {
        NotificationCenter.default.removeObserver(self, name: .UIKeyboardWillShow, object: nil)
    }
}

class blankView:UICollectionReusableView{

}

extension UICollectionView{
    func reloadItems(inSection section:Int = 0) {
        print("made it to reload")
        for i in 0..<self.numberOfItems(inSection: section){
        self.reloadItems(at: [IndexPath(item: i, section: section)])
        }
    }
}

Answer 1

您正在向VC.currentTagsArray 添加一个新字符串，但您没有在集合视图上调用insertItems(at:)，因此当numberOfItemsInSection 突然开始返回比以前更多的项目时，您会得到一致性异常。

关于风格的其他一些观察：

• 我会使用委托将事件传递回视图控制器，而不是让标题视图和单元格持有对 VC 的引用并紧密耦合对象。
• 变量VC 应该是vc。大写首字母是一个类
• 就叫它currentTags而不是currentTagsArray

Answer 2

您的问题是因为您只调用insertItemsAt，它正是这样做的，插入了一个项目。您忘记了deleteItemsAt，这应该会删除您不想再显示的所有项目。

顺便说一句，您真的应该考虑重构您的代码。它不容易阅读，而且事情没有在正确的地方完成。例如，您的标题永远不应该是负责更新您的收藏视图的人。您应该将其留给控制器本身并使用委托将文本从标题获取到视图控制器。

更新

这是为您进行搜索的完整代码。这只是一个示例，因此您可以了解它是如何完成的。

import UIKit

class ViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource, UICollectionViewDelegate, UISearchBarDelegate {

    lazy var collectionView : UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
        cv.backgroundColor = .white
        cv.delegate = self
        cv.dataSource = self
        return cv
    }()

    var genericTagsArray:[String] = ["tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za","tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za"]

    var currentTagsArray:[String] = [String]() {
        didSet {
            collectionView.reloadSections(IndexSet.init(integer: 1))
        }
    }


    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.addSubview(collectionView)
        collectionView.register(Cell.self, forCellWithReuseIdentifier: "cell")
        collectionView.register(Header.self, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "header")
        collectionView.anchor(top: view.safeAreaLayoutGuide.topAnchor, leading: self.view.leadingAnchor, bottom: self.view.bottomAnchor, trailing: self.view.trailingAnchor, padding: .init(top: 0, left: 0, bottom: 0, right: 0))
        collectionView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0)


    }


    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        if section == 0 { return 0 }
        return currentTagsArray.count
    }

    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 2
    }

    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        let header = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "header", for: indexPath) as! Header
        header.searchBar.delegate = self
        return header
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
        if section == 0 {
            return CGSize(width: self.view.frame.width, height: 50)
        }
        return CGSize()
    }


    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! Cell
        cell.label.text = currentTagsArray[indexPath.item]
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

        return CGSize(width: self.view.frame.size.width, height: 50)

    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 5
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 5
    }

    func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
        self.currentTagsArray = self.genericTagsArray.filter { (text) -> Bool in
            return text.contains(searchText.lowercased())
        }
    }
}

class Cell : UICollectionViewCell {

    let label = UILabel()

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupViews()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setupViews() {
        self.backgroundColor = .gray
        self.addSubview(label)
        label.anchor(top: self.topAnchor, leading: self.leadingAnchor, bottom: self.bottomAnchor, trailing: self.trailingAnchor)
    }

}

class Header : UICollectionViewCell {

    let searchBar = UISearchBar()

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupViews()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func setupViews() {
        self.backgroundColor = .gray
        self.addSubview(searchBar)
        searchBar.anchor(top: self.topAnchor, leading: self.leadingAnchor, bottom: self.bottomAnchor, trailing: self.trailingAnchor)
    }

}

extension UIView {
    func anchor(top: NSLayoutYAxisAnchor?, leading: NSLayoutXAxisAnchor?, bottom: NSLayoutYAxisAnchor?, trailing: NSLayoutXAxisAnchor?, padding: UIEdgeInsets = .zero, size: CGSize = .zero) {
        translatesAutoresizingMaskIntoConstraints = false

        if let top = top {
            topAnchor.constraint(equalTo: top, constant: padding.top).isActive = true
        }

        if let leading = leading {
            leadingAnchor.constraint(equalTo: leading, constant: padding.left).isActive = true
        }

        if let bottom = bottom {
            bottomAnchor.constraint(equalTo: bottom, constant: -padding.bottom).isActive = true
        }

        if let trailing = trailing {
            trailingAnchor.constraint(equalTo: trailing, constant: -padding.right).isActive = true
        }

        if size.width != 0 {
            widthAnchor.constraint(equalToConstant: size.width).isActive = true
        }

        if size.height != 0 {
            heightAnchor.constraint(equalToConstant: size.height).isActive = true
        }
    }
}