Swift TagCloudCollectionView

TagCloudCollectionView.swift

//: A UIKit based Playground for presenting user interface
  
import UIKit
import PlaygroundSupport

class EdgeInsetLabel: UILabel {
    private let textInsets: UIEdgeInsets

    init(inset: UIEdgeInsets) {
        textInsets = inset
        super.init(frame: CGRect.zero)
    }

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

    override func textRect(forBounds bounds: CGRect, limitedToNumberOfLines numberOfLines: Int) -> CGRect {
        let insetRect = bounds.inset(by: textInsets)
        let textRect = super.textRect(forBounds: insetRect, limitedToNumberOfLines: numberOfLines)
        let invertedInsets = UIEdgeInsets(top: -textInsets.top,
                                          left: -textInsets.left,
                                          bottom: -textInsets.bottom,
                                          right: -textInsets.right)
        return textRect.inset(by: invertedInsets)
    }

    override func drawText(in rect: CGRect) {
        super.drawText(in: rect.inset(by: textInsets))
    }
}

class MyCell: UICollectionViewCell {
    
    lazy var titleLabel: UILabel = {
        let view = EdgeInsetLabel(inset: UIEdgeInsets(top: 0, left: 16, bottom: 0, right: 8))
        view.font = .systemFont(ofSize: 16)
        view.frame = self.contentView.frame
        view.backgroundColor = .systemFill
        self.contentView.addSubview(view)
        return view
    }()
    
    func set(title: String) {
        titleLabel.text = title
        clipsToBounds = true
    }
    
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        layer.cornerRadius = rect.height / 2
    }
}

class FlowLayout: UICollectionViewFlowLayout {
    
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let attributesForElementsInRect = super.layoutAttributesForElements(in: rect) else { return nil }
        var newAttributesForElementsInRect = [UICollectionViewLayoutAttributes]()
        // use a value to keep track of left margin
        var leftMargin: CGFloat = 0.0;
        var topMargin: CGFloat = 0.0;
        for refAttributes in attributesForElementsInRect {
            
            // If element on a next line
            if topMargin != refAttributes.frame.origin.y {
                topMargin = refAttributes.frame.origin.y
                leftMargin = self.sectionInset.left // Start from the begining
            }
            
            // Modify frame for current refAttributes
            var newLeftAlignedFrame = refAttributes.frame
            newLeftAlignedFrame.origin.x = leftMargin
            refAttributes.frame = newLeftAlignedFrame
            
            // Calculate for next element in a line
            leftMargin += refAttributes.frame.size.width + minimumInteritemSpacing
            newAttributesForElementsInRect.append(refAttributes)
        }
        return newAttributesForElementsInRect
    }
    
}

class MyViewController : UIViewController {
    
    var data = ["Aruba  ⤫", "Afghanistan  ⤫", "Africa  ⤫", "Angola  ⤫", "Albania  ⤫", "Andorra  ⤫", "Andean region  ⤫", "Arab World  ⤫", "United Arab Emirates  ⤫", "Argentina  ⤫", "Armenia  ⤫", "American Samoa  ⤫", "Antigua and Barbuda  ⤫"].shuffled()
    
    override func loadView() {
        let view = UIView()
        view.backgroundColor = .white
        let layout = FlowLayout()
        layout.scrollDirection = .vertical
        layout.minimumInteritemSpacing = 8
        layout.sectionInset = UIEdgeInsets(top: 8, left: 8, bottom: 8, right: 8)
        let collection = UICollectionView(frame: .zero, collectionViewLayout: layout)
        view.addSubview(collection)
        collection.register(MyCell.self, forCellWithReuseIdentifier: "cell")
        collection.backgroundColor = .systemGray4
        collection.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        collection.dataSource = self
        collection.delegate = self
        self.view = view
    }
}

extension MyViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        data.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
        if let cell = cell as? MyCell {
            cell.set(title: data[indexPath.item])
        }
        return cell
    }
}

extension MyViewController: UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        data.remove(at: indexPath.item)
        collectionView.deleteItems(at: [indexPath])
        collectionView.collectionViewLayout.invalidateLayout()
    }
}

extension MyViewController: UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let attributes = [ NSAttributedString.Key.font : UIFont.systemFont(ofSize: 16)]
        var size = data[indexPath.item].size(withAttributes: attributes)
        size.height = size.height + 16
        size.width = size.width + 32
        return size
    }
}

// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()