Using structs and enums in SwiftData models
Using structs and enums in SwiftData models 관련
Updated for Xcode 15
Any class marked with @Model can be used with SwiftData immediately, but you can also use any struct or enum as long as they conform to the Codable protocol. This works even if the enums have raw or associated values.
Important
Just because you can use them, it doesn’t mean you should. Please read this page fully before coming to a conclusion.
There are a couple of things you should be aware of when doing this, but first let’s look at a practical example. If you wanted to store a User record that has a status enum attached to it, you might write this:
enum Status: Codable {
case active
case inactive(reason: String)
}
@Model class User {
var name: String
var age: Int
var status: Status
init(name: String, age: Int, status: Status) {
self.name = name
self.age = age
self.status = status
}
}
SwiftData will store the whole enum case, along with the reason string attached to it.
Internally something interesting happens: SwiftData flattens the enum and its associated value directly into the database record for the User, rather than spinning it off into a separate table. This makes sense if you think about it: value types like structs and enums naturally only have a single owner, so there’s no need to create a relationship.
So, value-type properties become attributes in your underlying storage immediately. This works for all basic value types (Int, String, etc), but you can also also use structs, enums, Codable data, and collections of value types.
However, there is a catch: if you use collections of value types, e.g. [String], SwiftData will save that directly inside a single property too. Right now it’s encoded as binary property list data, which means you can’t use the contents of your array in a predicate.
If you attempt to do so, your app will just crash at runtime. So, please be very careful.
Of course, this behavior is an implementation detail of SwiftData, and is subject to change at any point in the future – do try it yourself before coming to a final conclusion.
