How to get value of specified field in an array of objects in mongodb

Question

I want to get values of specified field from the users array. Something like {_id: {$in: this.users}}. The difference is that users is an array of objects and I want to get the _id field of each object in this array. Here's a code sample:

var UserSchema = new Schema({
    username: {type: String, required: true, unique: true},
    password: {type: String, required: true,},
    email: {type: String, required: true, unique: true},
    role: {type: String, enum: ['user'], required: true},
    name: String,
    phoneNumber: Number,
    companies: [{
        _company: {type: Schema.ObjectId, ref: 'Company'},
        points: Number
    }],
    points: Number,
    created_at: Date,
    updated_at: Date
})

And I want write this middleware for mongoose UserSchema:

UserSchema.pre('remove', function(next) {
    this.model('Company').update(
        {_id: {$in: ??????????????????}},
        {$pull: {users: this._id}},
        next()
    )
})

But I don't know how to retrieve _company field from companies using $in.

Any help will be appreciated. Thanks.

Sory, I didn't change it after Copy-Paste. It should be another Schema. — kuba12
– kuba12, Commented Feb 29, 2016 at 14:34

zangw · Accepted Answer · 2016-02-29 14:41:54Z

1

Please try this

UserSchema.pre('remove', function(next) {
    var ids = this.companies.map(function(o) {return o._company;});
    this.model('Company').update(
        {_id: {$in: ids}},
    //...

answered Feb 29, 2016 at 14:41

zangw

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SiddAjmera · Accepted Answer · 2016-02-29 14:22:36Z

1

Ok so as far as I understood, you have an array named users, that has your User Objects. And you want to get just the _id field values from that array. So you can do something like this :

var ids = users.map(function(user){ return user._id });

Now that you have the _id values of the users, you can go ahead with your query.

answered Feb 29, 2016 at 14:22

SiddAjmera

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3 Comments

kuba12 Over a year ago

I have an array, named companies and there are my companies objects. What I want to get is _company field from array named companies.

SiddAjmera Over a year ago

Do this : var _companies = companies.map(function(company){ return company._company });

SiddAjmera Over a year ago

This will return the _company field from each object in your companies array.

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