Swift 3 optional parameters - swift

Question

Is it possible to create optional initialization parameters in Swift so I can create an object from JSON with the values returned from the API call, but then when I'm saving that object later I can also save the downloaded UIImage for one of the urls I got before.
Example:
class Story: NSObject, NSCoding {
var id: Int?
var title, coverImageURL: String?
var coverImage: UIImage?
required init?(anId: Int?, aTitle: String?, aCoverImageURL: String?) {
self.id = anId
self.title = aTitle
self.coverImageURL = aCoverImageURL
}
convenience init?(json: [String: Any]) {
let id = json["id"] as? Int
let title = json["title"] as? String
let coverImageURL = json["cover_image"] as? String
self.init(
anId: id,
aTitle: title,
aCoverImageURL: coverImageURL,
)
}
Then Later I want to save objects to memory
//MARK: Types
struct PropertyKey {
static let id = "id"
static let title = "title"
static let coverImageURL = "coverImageURL"
static let coverImage = "coverImage"
}
//MARK: NSCoding
func encode(with aCoder: NSCoder) {
aCoder.encode(id, forKey: PropertyKey.id)
aCoder.encode(title, forKey: PropertyKey.title)
aCoder.encode(coverImageURL, forKey: PropertyKey.coverImageURL)
aCoder.encode(coverImage, forKey: PropertyKey.coverImage)
}
required convenience init?(coder aDecoder: NSCoder) {
guard let id = aDecoder.decodeObject(forKey: PropertyKey.id) as? Int else {
os_log("Unable to decode the id for a Story object.", log: OSLog.default, type: .debug)
return nil
}
guard let title = aDecoder.decodeObject(forKey: PropertyKey.title) as? String else {
os_log("Unable to decode the title for a Story object.", log: OSLog.default, type: .debug)
return nil
}
let coverImageURL = aDecoder.decodeObject(forKey: PropertyKey.coverImageURL) as? String
let coverImage = aDecoder.decodeObject(forKey: PropertyKey.coverImage) as? UIImage
self.init(
anId: id,
aTitle: title,
aCoverImageURL: coverImageURL,
coverImage: coverImage,
)
}
Does this make sense? I want to be able to save a Story object as soon as I get the response from the API, but later when I save the story to memory, I want to be able to save the fetched UIImage for the coverImage.
How would I do that?

Answer 1

I'm not sure why no one took the easy points on this answer, but the answer is to simply make your properties optionals, and then you can set them with a value, or nil. You can also create convenience initializers that automatically set certain values to nil if you want. So, using my app as an example, I have a model that gets built from an API call. that model has values like id, created_at, etc that don't exist until a record is saved to the server, but I create objects locally, store them, and eventually send them to the server, so I need to be able to set the above values only when creating an object from JSON, so here is what I did:
class Story: NSObject, NSCoding {
var id: Int?
var title, coverImageURL: String?
var coverImage: UIImage?
required init?(anId: Int?, aTitle: String?, aCoverImageURL: String?) {
self.id = anId
self.title = aTitle
self.coverImageURL = aCoverImageURL
}
convenience init?(json: [String: Any]) {
let id = json["id"] as? Int
let title = json["title"] as? String
let coverImageURL = json["cover_image"] as? String
self.init(
anId: id,
aTitle: title,
aCoverImageURL: coverImageURL,
)
}
convenience init?(aTitle: String, aCoverImage: UIImage?) {
let title = aTitle
let subtitle = aSubtitle
let coverImage = aCoverImage
let isActive = activeStatus
self.init(
anId: nil,
aTitle: title,
aCoverImageURL: nil,
aCoverImage: coverImage,
)
}
As you can see, I only set two of the values when I'm creating an object locally, and the other values are just set to nil. To allow a value to be set to nil, just make it an optional when setting it. Simple!