BadgePosition.swift

BadgePosition.swift

import UIKit

enum BadgePosition {
    case topRight
    case topLeft
    case bottomRight
    case bottomLeft
    case center
}

class BadgeLabel: UILabel {
    
    private let padding: CGFloat = 6.0

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

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }

    private func setup() {
        backgroundColor = .red
        textColor = .white
        font = UIFont.systemFont(ofSize: 12, weight: .bold)
        textAlignment = .center
        clipsToBounds = true
        isHidden = true
        translatesAutoresizingMaskIntoConstraints = false
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        layer.cornerRadius = bounds.height / 2
    }
    
    override var intrinsicContentSize: CGSize {
        let labelSize = super.intrinsicContentSize
        let dimension = max(labelSize.width, labelSize.height) + padding
        return CGSize(width: dimension, height: dimension)
    }

    func updateBadge(number: Int) {
        if number <= 0 {
            isHidden = true
        } else {
            isHidden = false
            text = "\(number)"
            invalidateIntrinsicContentSize()
        }
    }
    
    func position(_ position: BadgePosition, _ padding: CGFloat) {
        guard let view = superview else { return }
        
        NSLayoutConstraint.deactivate(view.constraints.filter {
            $0.firstItem === self || $0.secondItem === self
        })
        
        switch position {
        case .topRight:
            NSLayoutConstraint.activate([
                topAnchor.constraint(equalTo: view.topAnchor, constant: padding),
                trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -padding)
            ])
        case .topLeft:
            NSLayoutConstraint.activate([
                topAnchor.constraint(equalTo: view.topAnchor, constant: padding),
                leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: padding)
            ])
        case .bottomRight:
            NSLayoutConstraint.activate([
                bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -padding),
                trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -padding)
            ])
        case .bottomLeft:
            NSLayoutConstraint.activate([
                bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -padding),
                leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: padding)
            ])
        case .center:
            NSLayoutConstraint.activate([
                centerXAnchor.constraint(equalTo: view.centerXAnchor),
                centerYAnchor.constraint(equalTo: view.centerYAnchor)
            ])
        }
    }
    
}

private var badgeKey: UInt8 = 0
extension UIView {
    
    private var badge: BadgeLabel? {
        get {
            return objc_getAssociatedObject(self, &badgeKey) as? BadgeLabel
        }
        set {
            objc_setAssociatedObject(self, &badgeKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }

    func badge(number: Int, position: BadgePosition, padding: CGFloat = 0) {
        if badge == nil {
            let badgeLabel = BadgeLabel()
            addSubview(badgeLabel)
            badge = badgeLabel
        }
        badge?.updateBadge(number: number)
        badge?.position(position, padding)
    }
    
}