Hello All, some background information first. I have the following struct: Struct Category: Identifiable, Codeable, Hashable { var id: UUID var name: String var subCategory: [Category]? } var categories: [Category] There is no limit how many levels deep the subcategory can be. The user is essentially creating a hierarchical data filing system. Given that the number of subCategory levels is unlimited, I am recursing over the subcategories to find the correct level at which to insert the newCategory. The recursive function to add category is declared as: func recursiveAddCategory(newCategory: Category, subCategoryOf: inout [Category]?) you will note that I am trying to pass the subCategory as a reference (using inout), so that I can add to the original and the function is called as recursiveAddCategory(newCategory, &categories.subCategory!) the actual append statement within the recursiveAddCategory function is: categories.subCategory?.append(newCategory) I am encountering no errors but also find that the newCategory is not being added to the categories array. Any help or guidance appreciated. Thanks