UIImage 的 extension 用来通过枚举项来初始化图片资源

gistfile1.swift

// www.swiftcafe.io  更多技术内容
extension UIImage {

    enum AssetIdentifier : String {

        case Flower = "ic_flower"
        case Mushroom = "ic_mushroom"
        case Mario = "ic_mario"

    }

    convenience init!(assetIdentifier : AssetIdentifier) {

        self.init(named: assetIdentifier.rawValue)

    }

}