CODEWITHSUNDEEP
javascriptmeteor
Brandon
Brandon

Reputation: 319

What is the difference between setting a Session's variable and Meteor Streams?

I'm a Meteor newbie. I came across the Meteor Streams package which allows for "Real Time messaging for Meteor". Here's what it can do:

Meteor Stream is a distributed EventEmitter across meteor. It can be managed with filters and has a good security model (Inherited from existing meteor security model). You can create as many as streams you want, and it is independent from mongo.

With Meteor Streams, you can communicate between

client to clients server to clients client to server server to servers

There's an example of it being used in a realtime blackboard where users can draw together. Being a Meteor newbie, out of ignorance, I ask, what is the difference between using something like this and just updating a session ie Session.set, Session.get. As I've seen session being used, two browsers can be open and updated with the same information with Session.set. So in an environment where two people are drawing, why can't it just be done using Session setting vs Meteor collections or Streams? what is it I'm not understanding about Session setting? I believe I'm probably wrong thinking session setting could be used instead, I just would like to know why. It will help me to understand Sessions in Meteor and the Meteor Streams package.

Upvotes: 0

Views: 452

Answers (1)

Tarang
Tarang

Reputation: 75975

A Session variable is a quick variable created so you can reactively change stuff in templates.

E.g you have this in your template:

<template name="hello">
    {{message}}
</template>

With it a template helper

Template.hello.message = function() { return Session.get("message") }

If you do something like Session.set("message", "Hi there"), the html will say Hi there. The idea is that you can easily change your HTML using this. Its a type of one way data binding.

A Meteor stream helps you communicate between the browser and server (or other combinations between servers and clients) so you can send messages to and fro, but it wont help you change the HTML.

Likewise the Session wont help you communicate between the browser and server, it can help change HTML when you have a result in your events or pass data reactively between your javascript code and the html that the user sees.

With the blackboard example, you can share the data the other users have drawn, but it wont help you draw onto your blackboard. (In the case of blackboard you could use streams because you're updating a canvas with javascript, so you don't need a session). You cant use Session on its own (or dont need to since its a canvas) - but you need Meteor streams to communicate to the other users.

You could use stuff like JQuery to update your html too! Using a Session is by far the easiest though, because you can use it all over and only have to update one thing for all the rest to change.

Upvotes: 3

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