Automatically increase property value in Strongloop loopback model

Question

Is there a built-in way to automatically increase the value of a model property, is this Strongloop loopback? This model has a property called orderNumber, and I want it to start at 1 and increment by 1 each time a new model is created. This model is stored in the Mongo database. If loopback Strongloop doesn't have a built-in way, then what would be considered best practice using javaScript, Node and mongoDB?

Thanks,

Answer 1

Ok, this solution works, but I bypass Loopback and the "mongoDB connector". That's what I'm doing.

For a model called Sequence that looks like this:

{ "_id": { "$oid": "54ab3ec0cc074e24144f26d7" }, "collection": "SpecialOrder", "value": 113 } 

I'm doing it:

 mongoConnector = app.dataSources.MyMongoDBConnectorName.connector; mongoConnector.collection("Sequence").findAndModify({collection: 'SpecialOrder'}, [['_id','asc']], {$inc: { value: 1 }}, {new: true}, function(err, sequence) { if(err) { console.log(err.message); } else { // Do what I need to do with new incremented value sequence.value } }); 

There seems to be a built-in way for LoopbackJS to do this. A lot to go through to increase the value.

Thanks,

Warren bell

Answer 2

Have the same problem, but with Postgres. Fixed using only one id column identifier manually in the database (set the type to SERIAL, which means automatic growth in Postgres). I think the problem can be solved this way in any database.

Answer 3

I want to share my approach, similar to the answer of the author, but using Loopback methods. Here is the Sequence model I created:

 { "name": "sequence", "base": "PersistedModel", "idInjection": true, "options": { "validateUpsert": true }, "properties": { "name": { "type": "string", "required": true }, "value": { "type": "number", "required": true } }, "validations": [], "relations": {}, "acls": [], "methods": [] } 

In this model, you can save as many sequences as you want. Then I create the sequence I need with this script (in this case, the order sequence):

 var app = require('./server/server'); var Sequence = app.models.Sequence; Sequence.findOrCreate({ where: { name: 'order' } }, { name: 'order', value: 0 }, function (err) { if (err) { console.log(err); } process.exit(); }); 

Now, every time I need an order number to create an order, first I update the order entry in the model's Sequence , increasing its value , and then use it:

 var Sequence = Order.app.models.Sequence; Sequence.findOne({ where: { name: 'order' } }) .then(function (orderNumber) { orderNumber.value++; return orderNumber.save(); }) .then(function (orderNumber) { Order.upsert({ orderNumber: orderNumber.value, ... }); }); 

Hooray!