Add Created By, Updated By, Created Date, Updated Date to Model via Mixin in Loopback

Adding a created by, created date and updated by, updated date is always needed in Models. So why don’t we use a common Mixin for that.

We’ll create a Mixin which will do the job for your Models without copying and pasting the same code in every model.

READ =:> MySql Like Auto Increment Numeric Primary Key For Loopback with MongoDB

Create a file named “created-modified-injection.js” in common/mixins/ folder. and add the bellow code

//created-modified-injection.js
module.exports = function(Model, options) {
    'use strict';
    Model.defineProperty('created_by', {type: Number});
    Model.defineProperty('updated_by', {type: Number});
    Model.defineProperty('created_date', {type: Date});
    Model.defineProperty('updated_date', {type: Date});    
    Model.observe('before save', function event(ctx, next) {
        const token = ctx.options && ctx.options.accessToken;
        const userId = token && token.userId;
        let date = new Date();
        if (ctx.instance) {
            if (ctx.isNewInstance) {
                ctx.instance.created_by   = ctx.instance.created_by || userId;
                ctx.instance.created_date   = date;
            }else{
                ctx.instance.updated_by   = ctx.instance.updated_by || userId;
                ctx.instance.updated_date   = date;
            }
        }
next();
    });
};

This Will add created_by, created_date at the time of creating a new instance of the model and will add updated_by, updated_date while updating the instance in every model you enable the mixin in.

Now Enable the Mixin in the Model by adding the bellow property in your model.json files

"mixins": {
    "CreatedModifiedInjection": true
  },

That’s all! Comment if you have anything in mind.