CODEWITHSUNDEEP
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JAHelia
JAHelia

Reputation: 7922

SwiftUI: data identifier stability and uniqueness

At minute 33:00 of Demystify SwiftUI WWDC21 video, Raj talked about the importance of using a stable & unique identifier for the data model that will be rendered in a SwiftUI view, so using something like this is not recommended:

enter image description here

but something like this is a best practice:

enter image description here

I have regular data model structs (not persisted to disk or CoreData) that I need to render their data in SwiftUI views, how to create unique and stable IDs for those models ?

Upvotes: 0

Views: 754

Answers (2)

vadian
vadian

Reputation: 285079

It's not clearly mentioned in the WWDC video but an unique identifier is supposed to be a constant.

struct Pet : Identifiable {
    let id = UUID()
}

If the struct is being created from JSON with Decodable just add CodingKeys to exclude the identifier

struct Pet : Decodable, Identifiable {
    let id = UUID()
    let name : String

    private enum CodingKeys : String, CodingKey { case name }
}

Anyway use constants whenever possible.

Upvotes: 1

Raja Kishan
Raja Kishan

Reputation: 18914

You have to use a stored property instead of computed property.

as mention in docs.swift.org

computed properties, which don’t actually store a value. Instead, they provide a getter and an optional setter to retrieve and set other properties and values indirectly.

It means when using computed properties as their value change each time you are calling them.

So use stored property like this

struct Model {
    var id: UUID = UUID()
}

As the computed property is that runs code again and give you to new result.

Upvotes: 1

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