WCSession技术疑问：transferUserInfo与sendMessage该如何选择？

Hey there! Let's break down your two questions clearly:

1. Data Volume Limits: transferUserInfo() vs sendMessage() #

The two methods have distinct differences in their data size limits, tailored to their intended use cases:

• sendMessage(): This method is built for small, real-time payloads, so it has a strict data limit—usually capped at a few KB (e.g., around 4KB on iOS). It's ideal for sending short commands or tiny updates, but will fail if you try to send larger datasets like your user list.
• transferUserInfo(): Designed for bulk data transfers, this method supports much larger payloads (often up to tens of MB). It's perfect for sending arrays of dictionaries like your user list, even when the app is in the background, since the system will prioritize completing the transfer when resources are available.

2. Is It Okay to Use transferUserInfo() Without Leveraging FIFO? #

Absolutely! The FIFO (First-In-First-Out) queue behavior of transferUserInfo() is an optional feature, not a requirement. You can safely use this method to send single batches of your user list without relying on queue ordering. Here are a few key notes to keep in mind:

• Each call to transferUserInfo() creates an independent background transfer task. The system will handle it on its own timeline, so you don't have to worry about unintended ordering (since you don't need it anyway).
• Ensure all elements in your dictionary array are serializable (e.g., strings, numbers, data objects). Custom objects need to be converted to serializable formats (like JSON data) or implement serialization protocols (e.g., NSCoding on iOS) to avoid transfer failures.
• From a resource perspective, using transferUserInfo() for your user list is actually a better fit than sendMessage() if your dataset is large. Even without FIFO, it's optimized for transferring bulk data efficiently in the background.

Quick Recap #

If your user list is large enough to exceed sendMessage()'s limits, stick with transferUserInfo()—it works perfectly fine without using its FIFO queue. If your dataset is tiny, switching to sendMessage() is an option, but make sure you stay within its size constraints.

内容的提问来源于stack exchange，提问作者Tentacool7