Episode #540

Fixing Persistent Sorting

Series: Todo App in SwiftUI

11 minutes
Published on October 14, 2022

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In this episode we fix an issue that caused our sorting logic to be lost after adding persistence.

Todo Row Binding

    private func todoRowBinding(todo: Todo) -> Binding<Todo> {
        .init(get: {
            todo
        }, set: { mutatedTodo in
            let isToggleChange = mutatedTodo.isCompleted != todo.isCompleted
            if isToggleChange {
                handleToggleChange(mutatedTodo)
            } else {
                controller.update(mutatedTodo)
            }
        })
    }

Move And Update Indices


private func move(todos: inout [Todo], from source: IndexSet, to destination: Int) {
    todos.move(fromOffsets: source, toOffset: destination)
    todos.indices.forEach {
        todos[$0].sortOrder = $0
    }
}

Handle Toggle Change

private func handleToggleChange(_ todo: Todo) {
    guard let originalIndex = todos.firstIndex(where: { $0.id == todo.id }) else {
        controller.update(todo)
        return
    }
    var copy = todos
    copy[originalIndex] = todo
    for index in todos.indices.reversed() where index != originalIndex {
        if todos[index].isCompleted {
            continue
        }
        move(todos: &copy, from: .init(integer: originalIndex), to: index + 1)
        break
    }
    withAnimation {
        todos = copy
        controller.updateAll(copy)
    }
}

This episode uses Boutique 2.0, Xcode 14.0, Swift 5.7.