useful.swift

class StickerBrowserViewController: MSStickerBrowserViewController {

    let stickerNames = ["piggie_cute", "piggie_bowing", "piggie_waving", "piggie_crying", "piggie_laughing", "piggie_winking", "professor_pig", "piggie_cheering", "piggie_scorning", "piggie_swooning", "wtf", "870194"]
    var stickers = [MSSticker]()
    weak var delegate: StickerBrowserViewControllerDelegate?

    override func viewDidLoad() {

        super.viewDidLoad()
        loadStickers()
    }

    override var stickerSize: MSStickerSize {
        get {
            return .regular
        }
    }

    func loadStickers() {

        stickers = stickerNames.map( {name in
            let url = Bundle.main.url(forResource: name, withExtension: "png")!
            return try! MSSticker(contentsOfFileURL: url, localizedDescription: name)
        })  
    }
}

extension StickerBrowserViewController {

    override func numberOfStickers(in stickerBrowserView: MSStickerBrowserView) -> Int {
        return stickers.count
    }

    override func stickerBrowserView(_ stickerBrowserView: MSStickerBrowserView, stickerAt index: Int) -> MSSticker {
        return stickers[index]
    }
}