Hex Color Parsing in Swift: Cache UIColor for Speed

If your UI rebuilds often, repeatedly converting the same hex strings to UIColor wastes CPU cycles.

Solution

Use a static dictionary cache keyed by normalized hex values, and return the cached color before parsing again.

import UIKit

extension UIColor {
    private static var hexColorCache: [String: CGColor] = [:]
    private static let cacheLock = NSLock()

    convenience init?(hex: String) {
        let cleanedHex = hex
            .trimmingCharacters(in: .whitespacesAndNewlines)
            .trimmingCharacters(in: CharacterSet.alphanumerics.inverted)
            .uppercased()

        Self.cacheLock.lock()
        if let cachedColor = Self.hexColorCache[cleanedHex] {
            Self.cacheLock.unlock()
            self.init(cgColor: cachedColor)
            return
        }
        Self.cacheLock.unlock()

        guard cleanedHex.count == 6,
              let rgbValue = UInt64(cleanedHex, radix: 16)
        else { return nil }

        let red = CGFloat((rgbValue >> 16) & 0xFF) / 255
        let green = CGFloat((rgbValue >> 8) & 0xFF) / 255
        let blue = CGFloat(rgbValue & 0xFF) / 255

        self.init(red: red, green: green, blue: blue, alpha: 1)

        Self.cacheLock.lock()
        Self.hexColorCache[cleanedHex] = self.cgColor
        Self.cacheLock.unlock()
    }
}

This optimization is most useful in reusable cells, dynamic theming, and frequently recomputed Swift/UIKit view trees.

When to Use

• You construct colors from the same hex strings repeatedly.
• You parse colors inside render/update paths.
• You need a low-effort optimization with minimal API changes.