Proper way to create models on the server - swift

Question

Consider the app don't store images within models. Instead, it stores URLs, which are used to retrieve images from image cache.
Consider this model:
class Post {
let id: String
let title: String
let imageUrl: URL
}
Let's say the user creates a new post (enters title and selects an image) and the app sends it over to the server.
Question: what is a proper way to write a method which creates a new post on the server?
I was thinking to write something like:
func createModel(_ model: Post, completion: () -> Void)
but the problem is the app doesn't know imageUrl yet.
Another thought was to have a method accepting all the properties of the model:
func createPost(_ title: String, image: UIImage, completion: () -> Void)
but this solution is not reusable: it's impossible to have a generic method for creating a model. Not good.
Also, this approach doesn't allow us to use the model while it's not saved to the backend yet, forcing to show the activity indicator.
Any suggestions how to deal with that?

Answer 1

If you really need immutable model (which I think you don't) then you can choose to save images in app's temporary directory and use the local images for all the newly created posts and server images for all other posts. This way your model will stay the same and you'll get rid of any activity indicator.
class Post {
let id: String
let title: String
var imageUrl: URL
init(id:String,title:String,imageUrl:URL){
self.id = id
self.title = title
self.imageUrl = imageUrl
}
init(id:String,title:String,image:UIImage){
self.id = id
self.title = title
let data = UIImageJPEGRepresentation(image, 0.8)
let url = URL(fileURLWithPath: "\(NSTemporaryDirectory())\(UUID().uuidString).jpeg")
try! data?.write(to: url, options: Data.WritingOptions.atomic)
self.imageUrl = url
}
}