How to define SwiftData models using the @Model macro 관련

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How to define SwiftData models using the @Model macro | SwiftData by Example

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How to define SwiftData models using the @Model macro

Updated for Xcode 15

You’ll use the @Model macro with all your SwiftData model classes. It automatically makes your class load and store from SwiftData, adds support for observing changes, and also adds conformances for Hashable, Identifiable, Observable, and PersistentModel.

In a simple case, your code looks like this:

@Model
class Employee {
    var name: String
    var emailAddress: String

    init(name: String, emailAddress: String) {
        self.name = name
        self.emailAddress = emailAddress
    }
}

That now becomes the source of truth for this data model – the complete definition of the data structure for that one type.

Important

The @Model macro requires your type be a class; it will not work on a struct.

Just marking the class with @Model automatically converts its stored properties into getters and setters that read/write the underlying SwiftData information, but it’s even smarter than that:

1. Whenever a SwiftUI view reads one of the properties of a SwiftData model object, it will automatically watch that property for changes so the view can be recreated as needed. If you previously used @Published and similar to annotate properties, that is not needed with SwiftData.
2. SwiftData quietly groups multiple changes together to save in one pass, so even if you do all sorts of inserting, deleting, and updating, they’ll be batched for maximum performance.
3. Whenever one of these batches completes, SwiftData automatically saves all its outstanding changes, so your data is always kept safe.
4. Any computed properties aren’t affected by the macro, and won’t be stored inside SwiftData persistent storage.

There are all sorts of ways to expand your models further. For example, we might say that every employee has a manager, like this:

@Model
class Employee {
    var name: String
    var emailAddress: String
    var manager: Employee?

    init(name: String, emailAddress: String, manager: Employee?) {
        self.name = name
        self.emailAddress = emailAddress
        self.manager = manager
    }
}

That introduces a one-to-one relationship: each manager has another manager, although it’s an optional Employee because someone at the very top of a company won’t have a manager. Relationships are covered in more detail later.

Another way we can add to our models is to add special attributes to individual properties. For example, we could say that every employee must have a unique email address:

@Model
class Employee {
    var name: String
    @Attribute(.unique) var emailAddress: String

    init(name: String, emailAddress: String) {
        self.name = name
        self.emailAddress = emailAddress
    }
}

SwiftData will enforce this rule for us automatically, ensuring that no two users have the same email address.

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이찬희 (MarkiiimarK)

Never Stop Learning.