Swift - check if string contains emoji character

EmojiCheck.swift

// https://stackoverflow.com/questions/30757193/find-out-if-character-in-string-is-emoji
import Foundation

extension UnicodeScalar {
    var isEmoji: Bool {
        switch value {
        case 0x1F600...0x1F64F, // Emoticons
             0x1F300...0x1F5FF, // Misc Symbols and Pictographs
             0x1F680...0x1F6FF, // Transport and Map
             0x1F1E6...0x1F1FF, // Regional country flags
             0x2600...0x26FF, // Misc symbols
             0x2700...0x27BF, // Dingbats
             0xE0020...0xE007F, // Tags
             0xFE00...0xFE0F, // Variation Selectors
             0x1F900...0x1F9FF, // Supplemental Symbols and Pictographs
             0x1F018...0x1F270, // Various asian characters
             0x238C...0x2454, // Misc items
             0x20D0...0x20FF: // Combining Diacritical Marks for Symbols
            return true

        default: return false
        }
    }

    var isZeroWidthJoiner: Bool {
        return value == 8205
    }
}

extension String {
    // Not needed anymore in swift 4.2 and later, using `.count` will give you the correct result
    var glyphCount: Int {
        let richText = NSAttributedString(string: self)
        let line = CTLineCreateWithAttributedString(richText)
        return CTLineGetGlyphCount(line)
    }

    var isSingleEmoji: Bool {
        return glyphCount == 1 && containsEmoji
    }

    var containsEmoji: Bool {
        return unicodeScalars.contains { $0.isEmoji }
    }

    var containsOnlyEmoji: Bool {
        return !isEmpty
            && !unicodeScalars.contains(where: {
                !$0.isEmoji && !$0.isZeroWidthJoiner
            })
    }

    // The next tricks are mostly to demonstrate how tricky it can be to determine emoji's
    // If anyone has suggestions how to improve this, please let me know
    var emojiString: String {
        return emojiScalars.map { String($0) }.reduce("", +)
    }

    var emojis: [String] {
        var scalars: [[UnicodeScalar]] = []
        var currentScalarSet: [UnicodeScalar] = []
        var previousScalar: UnicodeScalar?

        for scalar in emojiScalars {
            if let prev = previousScalar, !prev.isZeroWidthJoiner, !scalar.isZeroWidthJoiner {
                scalars.append(currentScalarSet)
                currentScalarSet = []
            }
            currentScalarSet.append(scalar)

            previousScalar = scalar
        }

        scalars.append(currentScalarSet)

        return scalars.map { $0.map { String($0) }.reduce("", +) }
    }

    fileprivate var emojiScalars: [UnicodeScalar] {
        var chars: [UnicodeScalar] = []
        var previous: UnicodeScalar?
        for cur in unicodeScalars {
            if let previous = previous, previous.isZeroWidthJoiner, cur.isEmoji {
                chars.append(previous)
                chars.append(cur)

            } else if cur.isEmoji {
                chars.append(cur)
            }

            previous = cur
        }

        return chars
    }
}