Issues with SwiftData One-to-Many Relationships

I've been working with SwiftData and encountered a perplexing issue that I hope to get some insights on.

When using a @Model that has a one-to-many relationship with another @Model, I noticed that if there are multiple class variables involved, SwiftData seems to struggle with correctly associating each variable with its corresponding data.

For example, in my code, I have two models: Book and Page. The Book model has a property for a single contentPage and an optional array of pages. However, when I create a Book instance and leave the pages array as nil, iterating over pages unexpectedly returns the contentPage instead.

You can check out the code for more details here. Has anyone else faced this issue or have any suggestions on how to resolve it? Any help would be greatly appreciated!

I dont understand. How does using appended help here? I am not adding anything to the array. Here is the summary

The following code defines two SwiftData models: Book and Page. In the Book class, there is a property contentPage of type Page, and an optional array pages that holds multiple Page instances.

@Model
class Book {
    var id = UUID()
    var title: String
    var contentPage: Page
    var pages: [Page]?
    
    init(id: UUID = UUID(), title: String, contentPage: Page) {
        self.id = id
        self.title = title
        self.contentPage = contentPage
        contentPage.book = self
    }
    
    func addPage(page: Page) {
        if pages == nil {
            pages = []
        }
        page.book = self
        pages?.append(page)
    }
}

enum PageType: String, Codable {
    case contentsPage = "Contents"
    case picturePage = "Picture"
    case textPage = "Text"
    case blankPage = "Blank"
}

@Model
class Page {
    var id = UUID()
    var pageType: PageType
    var pageNumber: Int
    var content: String
    var book: Book?
    
    init(id: UUID = UUID(), pageType: PageType, content: String, pageNumber: Int) {
        self.id = id
        self.pageType = pageType
        self.pageNumber = pageNumber
        self.content = content
    }
}

Observed Behavior: With the code above, I created a Book instance and populated all fields except for the pages, which was left as nil. However, when I attempt to iterate over the pages, I receive the contentPage instead. This indicates that there may be an issue with how SwiftData handles these associations.

Expected behavior - when iterating over pages I should not see contentPage since it is a separate property