Setters and Getters with Generics Swift

Question

I was wondering if there is a way to do this in a better way with generics. I have this singleton which needs a setter and another getter for every object. Plus, I have to check that the property is not nil in every getter, which is a lot of repeated code. ex:

class DataManager : NSObject {

    private override init(){}

    private var postData : [PostModel]?
    private var userData : [UserModel]?
    private var commentsData : [CommentsModel]?
    private var photosData : [PhotosModel]?
    private var albumsData : [AlbumsModel]?
    private var todosData : [TodosModel]?

    static let shared = DataManager()

    //MARK : Setters
    func setUserData(data : [UserModel]) {
        self.userData = data
    }

    func setPostData(data : [PostModel]) {
        self.postData = data
    }

    func setCommentsData(data : [CommentsModel]) {
        self.commentsData = data
    }

    func setAlbumsData(data : [AlbumsModel]) {
        self.albumsData = data
    }

    func setPhotosData(data : [PhotosModel]) {
        self.photosData = data
    }

    func setTodosData(data : [TodosModel]) {
        self.todosData = data
    }

    //MARK : Getters
    func getUserData() -> [UserModel]? {
        if self.userData != nil {
            return self.userData!
        }
        return nil
    }

    func getPostData() -> [PostModel]? {
        if self.postData != nil {
            return self.postData!
        }
        return nil
    }

    func getCommentsData() -> [CommentsModel]? {
        if self.commentsData != nil {
            return self.commentsData!
        }
        return nil
    }

    func getAlbumsData() -> [AlbumsModel]? {
        if self.albumsData != nil {
            return self.albumsData!
        }
        return nil
    }

    func getPhotosData() -> [PhotosModel]? {
        if self.photosData != nil {
            return self.photosData!
        }
        return nil
    }

    func getTodosData() -> [TodosModel]? {
        if self.todosData != nil {
            return self.todosData!
        }
        return nil
    }
}

I was wondering if all this logic could be done in one single method, maybe using generics?

Answer 1

If you want to force all object to set as a none optional and also get as a none optional , you don't need to define them as optional at the first place:

So instead of:

private var postData : [PostModel]?

you should have:

private var postData = [PostModel]()

This will gives you an empty none optional array and it can not be set or get as an optional .

---

If you want them to be nil before someone get them (for memory management or etc.), You can make them lazy :

private lazy var postData = [PostModel]()

So now postData will be nil until someone tries to read the value of it.

---

If you need to do some extra job when someone tries to set one of these, you can observe for changes before set and after set of the value:

private var postData = [PostModel]() {
    willSet { /* right before the value is going to set */ }
    didSet { /* right after the value is set */ } 
}

_{Note that lazy properties can not have observers}

---

So seems like you don't have any of the functions at all. And you can refactor your code to something like this:

class DataManager : NSObject {

    private override init(){}

    lazy var postData = [PostModel]()
    lazy var userData = [UserModel]()
    lazy var commentsData = [CommentsModel]()
    lazy var photosData = [PhotosModel]()
    lazy var albumsData = [AlbumsModel]()
    lazy var todosData = [TodosModel]()
}