Mongoose : using promises as parameters for other functions

Question

I am trying to get a good understanding of how to work with promises, mostly because I want to query data and then use that data to query other data

I have this Schema :

var serviceSchema = new Schema({
name: String,
});

And this method on it :

serviceSchema.statics.getIdByName = function getIdByName (serviceName) {

this.findOne({name :serviceName }).exec(function(err, service){
    if(err) console.log(err)

    return service._id

})
}

In my code I would like to do something like :

var service_id = Service.getIdByName("facebook")
otherSchema.findOne({service : service_id}).exec(...)

but service_id is a promise so the query isn't right, I don't want to be in callback hell and calling models inside of callbacks etc I have tried async with something like

async.series([getVariables], function(err, results){
otherSchema.findOne({service : service_id}).exec(...)})

Where getVariables is :

function getVariables(callback1) {
if(service_id!=undefined) {
    callback1(serviceID)
}}

Any help on how to achieve this is more than welcome! thanks a lot

Rahul Sharma · Accepted Answer · 2018-03-08 14:19:17Z

2

try this exec() returns promise.

serviceSchema.statics.getIdByName = function getIdByName(serviceName) {
    return this.findOne({
        name: serviceName
    }).exec();
}

Call getIdByName function

Service.getIdByName("facebook").then((data) => {
    console.log(data)
})

answered Mar 8, 2018 at 14:19

Rahul Sharma

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10 Comments

mtths Over a year ago

thanks a lot for your answer, this doesnt solve my problem because getIdByName is now only a findOne function and I can access the service's id only inside the 'then' where i would like to access it outside, stored in a variable i can pass as parameter to an other query does that mean i can only do that inside the 'then' ? isnt that callback hell, because in fact i have to get many ids before doing the query

Rahul Sharma Over a year ago

@mtths It'll not create callback hell because you can create the chain of promises, not callback hell.

Rahul Sharma Over a year ago

what did you try?

mtths Over a year ago

heres a more readable version : Service.findOne({name : 'JollyClick'}).then(function(service){ var service_id = service._id return Data.findOne({name : "Objectifs"}).exec() }) .then(function(data){ var objectifsID = data._id return Data.findOne({name : 'Personnalité'}).exec() }). then(function(data2){ var personnaliteID = data2._id DataUse.create({service : service_id, user : service_id, data : dataTypesIds}, function(err, datause){ }) cant access service_id when i want to create my document

Rahul Sharma Over a year ago

declare service_id outside .then and assign value inside .then.

var service_id; Service.findOne({         name: 'JollyClick'     }).then(function (service) {         service_id; = service._id         return Data.findOne({             name: "Objectifs"         }).exec();     })

|

mtths · Accepted Answer · 2018-03-29 13:54:10Z

0

The answer to this is actually using async/await and and do var x = await Model.findOne().exec()

or any function that returns a promise, then you can use x anywhere in the code

answered Mar 29, 2018 at 13:54

mtths

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