mongoose default value equal to other value

Question

For my project i've created an userSchema which simplified looks like the following:

var userSchema = new Schema({
    _id: String,
    screenname: {type: String, required: false, default: "equal _id"},
});

The user has an _id that is a string which also is his username. Everything works so far until i tried to add an extra field screenname. What i want is when the user creates an account, his screenname equals the value of _id. Later he can adjust it but by default it should equal the value of _id. i've also tried :

 screenname: {type: String, required: false, default: _id},

But than ofcourse _id is not defined.

How should i set the default value to equal another value ?

codeofnode · Accepted Answer · 2015-04-29 19:14:15Z

32

use the pre middleware explained here

userSchema.pre('save', function (next) {
    this.screenname = this.get('_id'); // considering _id is input by client
    next();
});

answered Apr 29, 2015 at 19:14

codeofnode

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Comments

ekerner · Accepted Answer · 2020-07-23 07:09:02Z

16

You can pass a function to default, following is a schema field excerpt:

username: {
    type: String,
    required: true,
    // fix for missing usernames causing validation fail
    default: function() {
        const _t = this as any; // tslint:disable-line
        return _t.name || _t.subEmail;
    }
},

answered Jul 23, 2020 at 7:09

ekerner

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3 Comments

gxmad Over a year ago

This worked wonderful for me,

@Prop({     type: String,     required: false,     default: function () {       return this.name || this.email.split('@')[0];     },   })   name: string;

Ram Over a year ago

There's a catch in this. You can not use arrow functions for the default value. For eg. the below code will always return the same value which is 7. default: () => Math.random(). // lets say output 0.7

Yaroslav Petrenko Over a year ago

@Ram as per latest version (7.5.0) you can use arrow functions. This code in my case generates random uuid's every time I call create: uuid: { type: String, default: () => crypto.randomUUID() }

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