salix/modules/ticket/back/models/ticket.js

const LoopBackContext = require('loopback-context');

module.exports = Self => {
    // Methods
    require('./ticket-methods')(Self);

    Self.observe('before save', async function(ctx) {
        const loopBackContext = LoopBackContext.getCurrentContext();
        const httpCtx = loopBackContext.active;

        if (ctx.isNewInstance) return;

        let changes = ctx.data || ctx.instance;

        if (changes.routeFk === null && ctx.currentInstance.routeFk != null) {
            let instance = JSON.parse(JSON.stringify(ctx.currentInstance));
            let userId = httpCtx.accessToken.userId;
            let logRecord = {
                originFk: ctx.currentInstance.routeFk,
                userFk: userId,
                action: 'delete',
                changedModel: 'Route',
                oldInstance: {ticket: instance.id},
                newInstance: null
            };
            await Self.app.models.RouteLog.create(logRecord);
        }
    });
};