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Command syntax

cursor.addListener(event, listener)

cursor.on(event, listener)

cursor.once(event, listener)

cursor.removeListener(event, listener)

cursor.removeAllListeners([event])

cursor.setMaxListeners(n)

cursor.listeners(event)

cursor.emit(event, [arg1], [arg2], [...])

Description

Cursors and feeds implement the same interface as Node’s EventEmitter.

Two events can be emitted, data and error.
Once you start using the EventEmitter interface, the other RethinkDB cursor commands like next, toArray, and each will not be available anymore.
The first time you call an EventEmitter method, the cursor or feed will emit data just after the I/O events callbacks and before setTimeout and setInterval callbacks.

Example: Broadcast all messages with socket.io.

r.table("messages").orderBy({index: "date"}).run(conn, function(err, cursor) {
    if (err) {
        // Handle error
        return
    }

    cursor.on("error", function(error) {
        // Handle error
    })
    cursor.on("data", function(message) {
        socket.broadcast.emit("message", message)
    })
});

This query can be rewritten with the each command:

r.table("messages").orderBy({index: "date"}).run(conn, function(err, cursor) {
    if (err) {
        // Handle error
        return
    }
    
    cursor.each(function(error, message) {
        if(error) {
            // Handle error
        }
        socket.broadcast.emit("message", message)
    })
});

Example: Broadcast all the messages inserted.

r.table("messages").changes().filter({old_val: null}).run(conn, function(err, feed) {
    if (err) {
        // Handle error
        return
    }

    feed.on("error", function(error) {
        // Handle error
    })
    feed.on("data", function(newMessage) {
        socket.broadcast.emit("message", newMessage)
    })
});

Related commands

next
each

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