Building A Task Component With Offline Sync

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Building a Task Component with Offline Sync

Hey guys! Today, we're diving deep into creating a robust task component with offline synchronization capabilities. This is gonna be super useful for any app where you want users to manage tasks seamlessly, even when they're not connected to the internet. Let's break down the plan step-by-step!

1. Data Model Setup: Laying the Foundation

First, we need to set up our data model. This involves defining how we'll store task information locally and how we'll handle synchronization with a remote database. We'll be using Core Data for local storage and Supabase as our backend.

Core Data Entities

We'll start by adding two entities to our Core Data model:

  • TaskItem: This entity will represent individual tasks. It includes the following attributes:
    • id: A unique identifier for the task (UUID).
    • text: The task description (String).
    • isCompleted: A boolean value indicating whether the task is completed (Bool).
    • order: An integer to define the order of tasks (Int16).
    • createdAt: The date and time when the task was created (Date).
    • updatedAt: The date and time when the task was last updated (Date).
    • userId: The ID of the user who owns the task (String).
    • needsSync: A boolean flag indicating whether the task needs to be synchronized with the server (Bool).
  • PendingOperation: This entity will help us manage offline synchronization. It stores information about operations that need to be performed on the server when the device is back online. Its attributes are:
    • id: A unique identifier for the pending operation (UUID).
    • operationType: A string indicating the type of operation (e.g., "create", "update", "delete") (String).
    • taskId: The ID of the task associated with the operation (UUID).
    • payload: A JSON string containing the data for the operation (String).
    • timestamp: The date and time when the operation was created (Date).

Supabase Table

On the Supabase side, we'll create a tasks table with corresponding columns for each attribute in the TaskItem entity. It's crucial to set up Row Level Security (RLS) policies to ensure that users can only access their own tasks. RLS is a powerful feature in Supabase that allows you to define fine-grained access control rules directly in the database.

By setting up this data model, we ensure that our app can store and manage tasks efficiently, both online and offline. The PendingOperation entity is particularly important for handling situations where the user makes changes while offline. These changes are stored locally and then synchronized with the server when the device regains connectivity. Setting up the backend correctly, especially with row level security, is paramount to protecting user data and preventing unauthorized access.

2. TaskViewModel: The Brain of the Operation

Alright, let's get into the TaskViewModel. This is where the magic happens – it's the central point for managing and manipulating our task data. Think of it as the brain that controls everything related to tasks in our app.

Published Tasks

First up, we have @Published var tasks: [TaskItem]. This is an array of TaskItem objects that the view observes. Whenever this array changes, the UI will automatically update to reflect the new task list. Using @Published from the Combine framework makes our data reactive and keeps the UI in sync with our data.

Task Management Functions

Next, we'll define functions to handle common task operations:

  • addTask(text:): Adds a new task with the given text.
  • updateTask(id:, text:): Updates the text of an existing task.
  • toggleComplete(id:): Toggles the completion status of a task.
  • deleteTask(id:): Deletes a task.

Each of these functions will interact with our Core Data store to perform the corresponding operation. Additionally, they'll need to create PendingOperation entries for offline synchronization. When a user adds, updates, or deletes a task while offline, we'll store these operations in the PendingOperation entity. This ensures that when the device comes back online, we can synchronize these changes with Supabase.

Synchronization Function

The syncWithSupabase() function is responsible for synchronizing local changes with the Supabase backend. This function will:

  1. Fetch all PendingOperation entries from Core Data.
  2. Process them in order, sending the corresponding requests to Supabase.
  3. Remove the PendingOperation entries after successful synchronization.
  4. Retry failed operations with exponential backoff.

To ensure that operations are processed in the correct order and to prevent conflicts, we'll use an operation queue. This queue will serialize the operations and execute them one at a time. If an operation fails, we'll retry it with a delay to handle transient network issues. Error handling is critical to ensure that no data is lost during synchronization.

Sorting Tasks

We'll sort the tasks in the following order:

  1. Incomplete tasks, sorted by their order attribute.
  2. Completed tasks, displayed last.

This sorting logic ensures that incomplete tasks are always displayed at the top of the list, making it easy for users to see what they need to focus on. Plus, completed tasks will be at the bottom, out of the way.

No Task Limit

Finally, there's no maximum limit to the number of tasks a user can add. This gives users the flexibility to manage as many tasks as they need without being restricted by arbitrary limits.

By implementing the TaskViewModel with these features, we create a robust and flexible system for managing tasks. The offline synchronization capabilities ensure that users can continue to work even when they don't have an internet connection. This makes the app more reliable and user-friendly. Remember, thorough testing is key to ensuring that the synchronization process works correctly and that no data is lost. We want to make it as user friendly as possible. That is why we don't have a task limit.

3. TaskComponent.swift: The Visual Representation

Let's move on to the TaskComponent.swift file. This is where we define the visual aspects of our task list. This component will be responsible for displaying the tasks and handling user interactions.

Size and Responsiveness

The width of the component will be set to 327pt. The height will be dynamic, displaying about 4 tasks in a collapsed state. This ensures that the component takes up a reasonable amount of screen space while still providing enough visibility to the task list. Responsiveness is key, so we want it to work on different screen sizes.

Expand and Collapse

Tapping the background of the component will toggle between expanded and collapsed states. In the expanded state, all tasks will be visible. In the collapsed state, only a few tasks will be shown, providing a more compact view.

Add Task Button

A plus icon (located in the top right corner, using the Documents/add.svg asset) will serve as the button to add new tasks. This provides a clear and intuitive way for users to create new tasks.

Empty State

When there are no tasks, we'll display an empty state with a dashed circle and the text "Add a task...". This provides a helpful visual cue to encourage users to start adding tasks.

Toast Messages

We'll use @State var showToast: Bool and @State var toastMessage: String to manage the display of toast messages. These messages will provide feedback to the user, such as confirming that a task has been deleted.

The TaskComponent brings together the data management provided by the TaskViewModel and the visual presentation of the task list. By carefully designing the layout and interactions, we can create a user-friendly and intuitive task management experience. Remember, the goal is to make it as easy as possible for users to add, view, and manage their tasks. We'll want to make sure this is as visually appealing as possible.

4. TaskRowView: Individual Task Presentation

Now, let's focus on the TaskRowView. This component is responsible for rendering each individual task in the list. It handles the display of the task text, completion status, and interactive elements.

Completion Toggle

A circle button will be used to toggle the completion status of a task. When a task is marked as complete, the text will be strikethrough, and the task will be moved to the bottom of the list. This provides clear visual feedback to the user and helps them keep track of their completed tasks.

Inline Editing

A TextField will allow users to edit the task text inline. Tapping on the text field will activate editing mode, allowing users to modify the task text directly in the list. This provides a seamless and efficient way to update tasks.

Context Menu

A long press gesture will trigger a context menu with a "Delete" option. This provides a convenient way for users to delete tasks. Context menus are a great way to provide additional options without cluttering the UI.

Deletion and Toast

When a user deletes a task, the task will be removed from the list, and a toast message will be displayed to confirm the deletion. The toast message will say "Task deleted". This provides feedback to the user and prevents accidental deletions.

By carefully designing the TaskRowView, we can create an intuitive and efficient way for users to interact with individual tasks. The inline editing and context menu options make it easy to update and delete tasks, while the completion toggle provides clear visual feedback. This is all about creating the best possible UX.

5. Toast Component: Providing Feedback

Let's talk about the Toast Component. This is a small notification overlay that appears at the bottom of the task component to provide feedback to the user. Toast messages are a great way to communicate information without interrupting the user's workflow.

Appearance and Behavior

The toast component will appear as a small overlay at the bottom of the task component. It will display a brief message, such as "Task deleted", to confirm that an action has been performed. The toast message will automatically dismiss after 2-3 seconds.

Animation

The toast component will use a slide-up animation to appear and disappear. This provides a smooth and visually appealing transition. Animations can add a touch of polish to the UI and make the app feel more responsive.

By using a toast component, we can provide timely feedback to the user without cluttering the UI. The auto-dismissing nature of toast messages ensures that they don't distract the user for too long. This is all about creating a seamless and user-friendly experience.

6. Offline Sync: Keeping Data Consistent

Now, let's dive into the heart of our task component: offline synchronization. This is what allows users to continue working even when they don't have an internet connection. The key is to ensure that any changes made offline are synchronized with the server when the device comes back online.

Operation Queue

We'll use an operation queue in Core Data to manage offline operations. When a user adds, updates, or deletes a task while offline, we'll create a PendingOperation entry in Core Data. This entry will contain the type of operation, the ID of the task, and the data associated with the operation.

The operation queue will process these PendingOperation entries in order. This ensures that changes are synchronized with the server in the correct sequence. If an operation fails, we'll retry it with exponential backoff to handle transient network issues.

Background Sync

When the app detects that the device is back online, it will automatically start synchronizing the PendingOperation entries with the Supabase backend. This background sync process will ensure that the local data is consistent with the server data.

Processing and Retrying

The synchronization process will involve sending requests to the Supabase API to create, update, or delete tasks. After each operation is successfully synchronized, the corresponding PendingOperation entry will be removed from Core Data. If an operation fails, it will be retried with a delay. The error handling is critical to ensure that no data is lost.

By implementing offline synchronization, we can provide a seamless experience for users, even when they're not connected to the internet. This makes the app more reliable and user-friendly. The PendingOperation entity and operation queue are essential for managing offline operations and ensuring that data is consistent.

7. Integration: Putting It All Together

Finally, let's talk about integrating our task component into the rest of the app. This involves adding the component to HomeView.swift, wiring up the AuthViewModel for user ID, and ensuring that the code complies with SwiftLint.

Adding to HomeView

The first step is to add the TaskComponent to HomeView.swift. This will involve creating an instance of the component and adding it to the view hierarchy. The component should be placed in a location that makes sense for the overall layout of the app.

Wiring AuthViewModel

Next, we need to wire up the AuthViewModel to provide the user ID to the TaskViewModel. This will allow the task component to load and save tasks for the currently logged-in user. Data protection should be a priority.

SwiftLint Compliance

Finally, we need to ensure that the code complies with SwiftLint. This involves running SwiftLint and fixing any violations that are reported. SwiftLint helps to enforce a consistent coding style and prevent common errors.

By integrating the task component into the rest of the app, we can create a seamless and cohesive user experience. The AuthViewModel ensures that the component is properly authenticated, and SwiftLint helps to maintain code quality. Attention to detail will produce better results.

Unresolved Questions

Network Reachability Library

One unresolved question is which network reachability library to use. Should we use NWPathMonitor or a third-party library? NWPathMonitor is a built-in framework that provides information about network connectivity. Third-party libraries may offer additional features or easier-to-use APIs.

Choosing the right network reachability library depends on the specific requirements of the app. If we only need basic connectivity information, NWPathMonitor may be sufficient. If we need more advanced features, such as the ability to detect specific types of network connections, a third-party library may be a better choice.

Well, there you have it! We've covered the entire plan for building a task component with offline synchronization. I hope this has been helpful and informative. Now go out there and start building!