SwiftUI: Why Is an Extension Used for a Custom Struct (Apple iOS App Dev Tutorial) – Ios swift

In the Apple [iOS App Dev Tutorial] (as of Jan 22)(https://developer.apple.com/tutorials/app-dev-training), under the Creating a Navigation Hierarchy section, we extend a struct that we have defined.

I have tried reading the Swift documentation about extensions, but don’t really understand why this is done here. The documentation talks about extending system types such as adding extra properties to the system type Double, but not adding extra properties to something that we have full control over, such as our own structure.

I am sure it is a best practice, as this is an Apple tutorial, but they don’t really do a good job of explaining it.

This is an example of the code they want you to write:

import SwiftUI

struct DailyScrum: Identifiable  {
    let id: UUID
    var title: String
    var attendees: [Attendee]
    var lengthInMinutes: Int
    var theme: Theme
    
    init(id: UUID = UUID(), title: String, attendees: [String], lengthInMinutes: Int, theme: Theme) {
        self.id = id
        self.title = title
        self.attendees = attendees.map { Attendee(name: $0) }
        self.lengthInMinutes = lengthInMinutes
        self.theme = theme
    }
}

extension DailyScrum {
    struct Attendee: Identifiable {
        let id: UUID
        var name: String
        
        init(id: UUID = UUID(), name: String) {
            self.id = id
            self.name = name
        }
    }
}

I am uncertain why the Attendee structure has to be defined within an extension. For example, this works too:

import SwiftUI

struct Attendee: Identifiable {
    let id: UUID
    var name: String
    
    init(id: UUID = UUID(), name: String) {
        self.id = id
        self.name = name
    }
}

struct DailyScrum: Identifiable  {
    let id: UUID
    var title: String
    var attendees: [Attendee]
    var lengthInMinutes: Int
    var theme: Theme
    
    init(id: UUID = UUID(), title: String, attendees: [String], lengthInMinutes: Int, theme: Theme) {
        self.id = id
        self.title = title
        self.attendees = attendees.map { Attendee(name: $0) }
        self.lengthInMinutes = lengthInMinutes
        self.theme = theme
    }
}

I’m just not sure why you would do one over the other.