CODEWITHSUNDEEP
node.jsrethinkdb
RocketFuel
RocketFuel

Reputation: 62

Increment and decrement RethinkDB Single Value

RethinkDB Increment and Decrement Single Value

Need some help, I'm learning Nodejs and Rethinkdb.

Currently I'm using this RethinkDB code to perform the Update operation.

r.table('items').get(id).update(item).run(self.connection, function(err, result) {
    if(result && result.replaced === 1) {
        res.send(item);
    }
    else if(err) {
        debug("[ERROR] updateItem %s:%s\n%s", err.name, err.msg, err.message);
        res.send({error: 'An error occurred when updating the item with id: ' + id});
    }
    else {
        debug("[ERROR] updateItem (%s): %j", id, result);
        res.send({error: 'An error occurred when updating the item with id: ' + id});
    }
});

Now the question is: How can i update a value in a row by Incrementing its value? For example lets say its about the stock of a car. so in a row i'll have:

    {
    "code":  "001" ,
    "brand":  "Ferrari" ,
    "stock":  "2"
    }

Now lets say I make a form to control how many cars will be added or removed from the stock. So for example let's say I want to add 3 new Ferraris. How can i update the value stock, incrementing the stock by 3 for a total of 5 and not replacing 2 for 3. Also lets say I sold 2 Ferraris, how can I decrease the value so the stock value will be 0.

And please excuse my poor English. Not my native language.

Upvotes: 0

Views: 714

Answers (1)

katafrakt
katafrakt

Reputation: 2488

If I understood correctly, here's what you can do. To add, use something like this:

r.table("items").get(id).update({
    stock: r.row("stock").add(2)
}).run(self.connection, callback);

To substract:

r.table("items").get(id).update({
    stock: r.row("stock").sub(3)
}).run(self.connection, callback);

Update

So, the values in the database are actually strings. You need to coerce them first. This should work:

r.table("items").get(id).update({
    stock: r.row("stock").coerceTo("number").add(2).coerceTo("string")
}).run(self.connection, callback);

Upvotes: 2

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