How I can delete the children of folder using CoreData?

Question

func deleteFolder(indexSet : IndexSet) {
    for folder in indexSet {
        let folderToDelete = folders[folder]
        
        do {
            coreDataService.context.delete(folderToDelete)
            try coreDataService.save()
            getFolders()
        } catch {
            print("Error = \(error)")
        }
    }
}

func deleteContent(indexSet : IndexSet) {
    for content in indexSet {
        let contentToDelete = contents[content]
        
        do {
            coreDataService.context.delete(contentToDelete)
            try coreDataService.save()
            getContetns()
        } catch {
            print("Error = \(error)")
        }
    }
}

I am trying to do data management by Coredata. There is 2 models, a folder and contents. the folder can have many contents, but the content is able to have only one folder.

I tried to delete a folder with onDelete using indexSet and succeeded with the function in my code. but I can't delete a content in a folder with that.

Could you let me know how I can do that?