how_to_build_threaded_messaging.md•5.12 kB
# How to Build Threaded Messaging Using PubNub
Threaded messaging, where replies are grouped under an initial message, is a common feature in chat applications. PubNub can be used to implement this functionality.
## Using PubNub Chat SDK
If you are building a chat application, the **PubNub Chat SDK** (available for various platforms) often has **built-in support for message threading**.
* **Recommendation:** If a Chat SDK with threading is available for your target platform, this is generally the easiest and most integrated way to implement threads.
* **Features:** These SDKs typically provide methods to:
* Send a message as a reply to an existing message.
* Fetch messages in a thread.
* Get thread participant information.
* Count replies in a thread.
* **How it works:** The Chat SDK usually handles the underlying message structuring and channel conventions needed for threading (e.g., by associating replies with a parent message's timetoken or a unique thread ID).
Consult the specific PubNub Chat SDK documentation for your platform to learn how to use its threading features.
## Implementing Threading Manually (with Core PubNub SDKs)
If you are using a core PubNub SDK (not a specialized Chat SDK) or need a custom threading implementation, you can build it by establishing conventions for how messages and their replies are structured and related.
**Common Approaches:**
1.
// Reply Message (example payload)
// {
// "text": "The deli on Main St is great!",
// "sender": "user_B",
// "parent_timetoken": "16170000001234567" // Links to parent
// }
```
* **Fetching Threads:** To display a thread, you would first fetch the parent message. Then, you could:
* Fetch all messages in the channel history and filter client-side for those whose `parent_timetoken` matches the parent message's timetoken. This can be inefficient for very active channels.
* Alternatively, use PubNub Functions and the KV Store or an external database: When a reply is published, a Function could store a mapping of `parent_timetoken` to an array of `reply_timetokens` (or reply message objects). Your client then queries this mapping (e.g., via an "On Request" Function) to get all replies for a parent.
* **Displaying Thread Indicators:** In your main channel view, if a message has replies (you'd know this if other messages reference its timetoken as `parent_timetoken`), display an indicator (e.g., "3 replies").
2. **Using a Unique Thread ID:**
* **Concept:** Assign a unique ID (e.g., a UUID) to each message that starts a new thread.
// Reply Message (example payload)
// {
// "text": "Yes, I'm available at 3 PM.",
// "sender": "user_D",
// "thread_id": "uuid_for_thread_1" // Belongs to the same thread
// }
```
* **Fetching Threads:** Similar to the timetoken approach, you can filter history client-side or use a backend/Function to maintain an index of messages belonging to each `thread_id`.
* This approach can be simpler if message timetokens are not easily accessible or if you want thread identifiers that are independent of PubNub's internal timetokens.
3. **Dedicated Channels per Thread (Less Common for General Chat):**
* **Concept:** When a message receives its first reply, a new, dedicated PubNub channel is created for that thread (e.g., `main_chat_channel:<parent_message_timetoken>_thread`). All subsequent replies are published to this dedicated thread channel.
* **Pros:** Clearly separates thread messages; fetching a thread is just subscribing to or getting history from its dedicated channel.
* **Cons:** Can lead to a very large number of channels. Might be more suitable for specific use cases like support tickets or focused discussions rather than a general chat feed with many small threads.
## Considerations for Manual Implementation
* **Data Storage/Indexing:** For efficient retrieval of threads, especially in high-volume channels, you'll likely need a backend mechanism (PubNub Functions + KV Store, or your own database) to index threads and their replies.
* **UI/UX:** How will you indicate that a message has a thread? How will users navigate into and out of threads?
* **Real-time Updates to Threads:** If a user is viewing a parent message, how will they see new replies arriving in real-time? They might need to be subscribed to an event (perhaps on the parent message's channel or a special notification channel) that signals a new reply has been posted to a thread they are interested in.
* **Message Ordering:** Ensure replies within a thread are displayed in chronological order (PubNub messages include timetokens which guarantee order within a channel's history).
Building threaded messaging manually requires careful planning of your data structures and how clients will publish and retrieve threaded conversations. If a PubNub Chat SDK with built-in threading is available, it's often the more straightforward path.