Rust: What is the difference between watch::Sender::send and watch::Receiver::borrow?

send — update value. borrow — read value.

send:

• Update shared state.
• Notify receivers.
• Only latest value.

borrow:

• Read current value.
• No blocking.
• Immutably.

1use tokio::sync::watch;
2
3let (tx, rx) = watch::channel("initial");
4
5tx.send("updated").unwrap();
6
7let value = rx.borrow();
8println!("{}", *value);  // "updated"

Key: send for updating, borrow for reading.