Ggtcf

I have been trying to collapse and expand the cells in collectionView when the section header is clicked but all the headers were expanding rather then the selected header.
This is my code

class ExampleHomeController: UICollectionViewController, UICollectionViewDelegateFlowLayout 

var expandedRow: Bool = false
var section: Int!

let postCellId = "postCellId"
let headerCellId = "headerCellId"

override func viewDidLoad() 
 super.viewDidLoad()

 collectionView.delegate = self
 collectionView.dataSource = self

 collectionView.backgroundColor = UIColor.init(r: 220, g: 214, b: 214)

 collectionView.register(PostCell.self, forCellWithReuseIdentifier: postCellId)
 collectionView.register(HeaderCell.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: headerCellId)



override func numberOfSections(in collectionView: UICollectionView) -> Int 
 return 4



override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int 
 return 3


override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell 
 let cell = collectionView.dequeueReusableCell(withReuseIdentifier: postCellId, for: indexPath)
 return cell


override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView 
 let header = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: headerCellId, for: indexPath) as! HeaderCell
 header.downArrowBtn.addTarget(self, action: #selector(showCells), for: .touchUpInside)
 return header



@objc func showCells() 
 if expandedRow == false 
 expandedRow = true
 else 
 expandedRow = false
 
 collectionView.reloadData()



func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize 
 if expandedRow == true 
 return CGSize(width: view.frame.width - 24, height: 280)
 else 
 return CGSize(width: view.frame.width - 24, height: 0)
 

And this is my Post Cell

class PostCell: UICollectionViewCell 
override init(frame: CGRect) 
 super.init(frame: frame)

 setupViews()


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


let postImage: UIImageView = 
 let view = UIImageView()
 view.image = #imageLiteral(resourceName: "one")
 return view
()


func setupViews() 

 backgroundColor = .white

 addSubview(postImage)

 postImage.anchor(top: contentView.topAnchor, leading: nil, bottom: contentView.bottomAnchor, trailing: nil, padding: .init(top: 20, left: 0, bottom: 0, right: 0), size: .init(width: 70, height: 0))
 postImage.centerXAnchor.constraint(equalTo: contentView.centerXAnchor).isActive = true

And this is my HeaderCell

class HeaderCell: UICollectionViewCell 

var expandedRow: Bool!

override init(frame: CGRect) 
 super.init(frame: frame)
 backgroundColor = UIColor.init(r: 220, g: 214, b: 214)
 setupViews()


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


let headerImage: UIImageView = 
 let view = UIImageView()
 view.image = #imageLiteral(resourceName: "facebook")
 return view
()

let headerLabel: UILabel = 
 let label = UILabel()
 label.text = "Posts By Network"
 return label
()

let downArrowBtn: UIButton = 
 let button = UIButton()
 button.setImage(#imageLiteral(resourceName: "downarrow"), for: .normal)
 button.imageView?.contentMode = .scaleAspectFit
 return button
()

func setupViews() 
 addSubview(headerImage)
 addSubview(headerLabel)
 addSubview(downArrowBtn)

 headerImage.anchor(top: contentView.topAnchor, leading: contentView.leadingAnchor, bottom: nil, trailing: nil, padding: .init(top: 8, left: 12, bottom: 0, right: 0), size: .init(width: 30, height: 30))
 headerLabel.anchor(top: headerImage.topAnchor, leading: headerImage.trailingAnchor, bottom: nil, trailing: nil, padding: .init(top: 2, left: 20, bottom: 0, right: 0))
 headerLabel.centerYAnchor.constraint(equalTo: headerImage.centerYAnchor).isActive = true
 downArrowBtn.anchor(top: headerLabel.topAnchor, leading: headerLabel.trailingAnchor, bottom: nil, trailing: contentView.trailingAnchor, padding: .init(top: 0, left: 0, bottom: 0, right: 12), size: .init(width: 20, height: 20))

All the cells were expanding when header is clicked, but I want to expand and collapse only the selected section, How can I do this. I am new to swift and have been trying this for past few weeks.
Thank you