Ios 如何继承PHAsset类并添加属性

AssetGridModel继承PHAsset类并添加isSelected属性

fileprivate var fetchResult: [AssetGridModel]!

let allPhotosOptions = PHFetchOptions()
        allPhotosOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        let fetchAssets = PHAsset.fetchAssets(with: allPhotosOptions)

或

为什么我出来的类型都是PHAsset，不是我写的继承类，也不能更改我添加的属性

请告诉我，谢谢你

使用运行时解决它

extension PHAsset {

    struct RuntimeKey {
        static var isSelectedKey = UnsafeRawPointer.init(bitPattern: "isSelectedKey".hashValue)
    }

    var isSelectedImage: Bool? {
        set {
            objc_setAssociatedObject(self, PHAsset.RuntimeKey.isSelectedKey, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
        }
        get {
            return objc_getAssociatedObject(self, PHAsset.RuntimeKey.isSelectedKey) as? Bool
        }
    }
}

extension PHAsset {

    struct RuntimeKey {
        static var isSelectedKey = UnsafeRawPointer.init(bitPattern: "isSelectedKey".hashValue)
    }

    var isSelectedImage: Bool? {
        set {
            objc_setAssociatedObject(self, PHAsset.RuntimeKey.isSelectedKey, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
        }
        get {
            return objc_getAssociatedObject(self, PHAsset.RuntimeKey.isSelectedKey) as? Bool
        }
    }
}