Meteor and MongoDB rerun helpers function

Question

I'm working on a project to manage the attendance of students in school.

The frontend runs with meteor. It displays the presence of all students from one class for the current day. The user (teacher) can switch the days back and forth, to make some changes.

Now I'm wondering how to rerun the helpers function for presentStudents when the selectedDate is changed.

The html code:


    
    Anwesenheit
    
    
    
    



    
        Anwesenheitliste
    

    
        
            
                
                    
                    
                
            
            
                
                
                
            
        
    

    
        
            
                
                    
                        {{#each presentStudents}}
                            {{> listingPresence}}
                        {{/each}}
                    
                        
                            
                            Vorname
                            Nachname
                            Beacon ID
                            1. Block
                            2. Block
                            3. Block
                            4. Block

The code from the server/main.js:

import { Meteor } from 'meteor/meteor';

const PresenceDB = new Mongo.Collection('studentsPresence');
const ListDB = new Mongo.Collection('studentsList');


function getDate(){
    let d = new Date();
    return d.getFullYear() + ('0' + (d.getMonth() + 1)).slice(-2).toString() + d.getDate().toString().slice(-2);
}

export function init(){
    const date = getDate();
    const match = PresenceDB.find({date: date}).fetch();
    if(match[0] == null) {
        const allStudents = ListDB.find().fetch();
        for (const student of allStudents){
            PresenceDB.insert({
                _id: newObjectID = new Mongo.ObjectID(),
                beaconID: student.beaconID,
                firstName: student.firstName,
                lastName: student.lastName,
                block1: false,
                block2: false,
                block3: false,
                block4: false,
                checkbox1: newObjectID1 = new Mongo.ObjectID(),
                checkbox2: newObjectID2 = new Mongo.ObjectID(),
                checkbox3: newObjectID3 = new Mongo.ObjectID(),
                checkbox4: newObjectID4 = new Mongo.ObjectID(),
                date: date
            });
        }

    }
}


Meteor.startup(() => {
    // code to run on server at startup
    init();
});

The code from the client/main.js:

import { Template } from 'meteor/templating';
import { ReactiveVar } from 'meteor/reactive-var';
// When this is imported the website doesn't load anymore!
//import { Session } from 'meteor/session';

import './main.html';

// Declare used collections
const PresenceDB = new Mongo.Collection('studentsPresence');
const ListDB = new Mongo.Collection('studentsList');

let selectedDate = getDate(0);

window.onload = function () {
    document.getElementById('current_date').textContent = getDate(1);
};

Date.prototype.addDays = function (n) {
    alert('Function got called!');
    let year = Number(selectedDate.slice(0, 4));
    let month = Number(selectedDate.slice(4, 6));
    let day = Number(selectedDate.slice(6, 8));
    if((day + n) > daysInMonth(month, year)) {
        month++;
        if(month < 1) {
            month = 12;
            year--;
        } if(month > 12) {
            month = 1;
            year++;
        }
        day = 0;
    }
    if((day + n) < 1) {
        month--;
        if(month < 1) {
            month = 12;
            year--;
        } if(month > 12) {
            month = 1;
            year++;
        }
        day = daysInMonth(month, year);
    } else {
        day = day + n;
    }
    document.getElementById('current_date').textContent = ('0' + day).slice(-2) + '.' + ('0' + month).slice(-2) + '.' + year;
    return '' + year + ('0' + month).slice(-2) + ('0' + day).slice(-2);
};

// Function for getting the number of days for a month depending on the month and year
function daysInMonth(month, year) {
    return new Date(year, month, 0).getDate();
}

// Function for getting today's date in the right format
function getDate(n){
    let d = new Date();
    if(n === 0) {
        // Return the date in the format: YYYYMMDD
        return d.getFullYear() + ('0' + (d.getMonth() + 1)).slice(-2).toString() + d.getDate().toString().slice(-2);
    } else {
        // Return the date in the format: DD.MM.YYYY
        return d.getDate().toString().slice(-2) + '.' + ('0' + (d.getMonth() + 1)).slice(-2).toString() + '.' + d.getFullYear();
    }
}

// Function for getting right time in the right format
function getTime(){
    let t = new Date();
    const time = t.getHours().toString() + t.getMinutes().toString();
    return parseInt(time, 10);
}

// Function to determine the current block lesson
function getBlock(time){
    let block = 0;
    if (745 < time && time < 915){
        block = 1;
    } else if (915 < time && time < 1100){
        block = 2;
    } else if (1100 < time && time < 1245){
        block = 3;
    } else if (1245 < time && time < 1800){
        block = 4;
    }
    return block;
}

// List students that are present today
Template.body.helpers({
    presentStudents: function() {
        //return PresenceDB.find({date: reactiveDate});
        return PresenceDB.find({date: selectedDate});
        //return PresenceDB.find({date: Session.get('sessionDate')});
    }
});

Template.body.events({
    // Update the presence for a scanned student for a specific lesson or create the document if necessary
    'submit .insertStudent': function(event) {
        const time = getTime();
        const currentBlock = getBlock(time);
        const userInput = event.target.beacon.value;
        const scannedStudent = ListDB.find(
            {beaconID: userInput},
            {firstName: 1, lastName: 1}
        ).fetch();
        const inPresenceList = PresenceDB.find(
            {beaconID: userInput, date: selectedDate},
            {_id: 1}
        ).fetch();
        let isExisting = (inPresenceList[0] != null);
        if (currentBlock !== 0){
            if (!isExisting){
                PresenceDB.insert(
                    {
                        _id: newObjectID = new Mongo.ObjectID(),
                        beaconID: userInput,
                        firstName: scannedStudent[0].firstName,
                        lastName: scannedStudent[0].lastName,
                        block1: false,
                        block2: false,
                        block3: false,
                        block4: false,
                        checkbox1: newObjectID1 = new Mongo.ObjectID(),
                        checkbox2: newObjectID2 = new Mongo.ObjectID(),
                        checkbox3: newObjectID3 = new Mongo.ObjectID(),
                        checkbox4: newObjectID4 = new Mongo.ObjectID(),
                        date: selectedDate
                    });
                const currentBlockString = 'block' + currentBlock;
                let obj = {};
                obj[currentBlockString] = true;
                PresenceDB.update(
                    {_id: newObjectID},
                    {$set: obj}
                );
            } else {
                const currentBlockString = 'block' + currentBlock;
                let obj = {};
                obj[currentBlockString] = true;
                PresenceDB.update(
                    {_id: inPresenceList[0]._id},
                    {$set: obj}
                );
            }
        } else {
            alert('Außerhalb der Schulzeiten!');
        }
        event.target.beacon.value = '';
        return false;
    },
    'click .previousDateClick': function(event) {
        //changeDate(0);
        let d = new Date();
        //selectedDate = d.addDays(0);
        Session.set('sessionDate', d.addDays(0));
        Session.set('sessionDate', 'TestSenf');
        alert(Session.get('sessionDate'));
    },
    'submit .nextDateClick': function(event) {
        //changeDate(1);
        let d = new Date();
        selectedDate = d.addDays(1);
        Session.set('sessionDate', selectedDate);
    }
});

Template.listingPresence.helpers({
    /*presentStudents: function() {
        // Here we get our template instance from Template.instance() and
        // can access showExtraFields from it.
        return Template.instance().reactiveDate.get();
    }*/
});

Template.listingPresence.onCreated(function(){
    // Here, this equals the current template instance. We can assign
    // our ReactiveVar to it, making it accessible throughout the
    // current template instance.
    this.reactiveDate = new ReactiveVar( selectedDate );
});

Template.listingPresence.events({
    'click .toggled1': function() {
        PresenceDB.update(this._id, { $set: {block1: !this.block1}})
    },
    'click .toggled2': function() {
        PresenceDB.update(this._id, { $set: {block2: !this.block2}})
    },
    'click .toggled3': function() {
        PresenceDB.update(this._id, { $set: {block3: !this.block3}})
    },
    'click .toggled4': function() {
        PresenceDB.update(this._id, { $set: {block4: !this.block4}})
    }
});

Meteor and MongoDB rerun helpers function

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