In Meteor, where do I model my business rules? - model-view-controller

Question

Beginner question : I've worked through the Try Meteor tutorial. I've got fields in my HTML doc, backed by helper functions that reference collections, and BOOM --> the fields are updated when the data changes in the DB.
With the "Hide completed" checkbox, I've also seen data-binding to a session variable. The state of the checkbox is stored in the Session object by an event handler and BOOM --> the list view is updated "automatically" by its helper when this value changes. It seems a little odd to be assigning to a session object in a single page application.
Through all this, my js assigns nothing in global scope, I've created no objects, and I've mostly seen just pipeline code, getting values from one spot to another. The little conditional logic is sprayed about wherever it is needed.
THE QUESTION... Now I want to construct a model of my business data in javascript, modelling my business rules, and then bind html fields to this model. For example, I want to model a user, giving it an isVeryBusy property, and a rule that sets isVeryBusy=true if noTasks > 5. I want the property and the rule to be isolated in a "pure" business object, away from helpers, events, and the meteor user object. I want these business objects available everywhere, so I could make a restriction, say, to not assign tasks to users who are very busy, enforced on the server. I might also want a display rule to only display the first 100 chars of other peoples tasks if a user isVeryBusy. Where is the right place to create this user object, and how do I bind to it from my HTML?

Answer 1

You can (and probably should) use any package which allows you to attach a Schema to your models.
Have a look at:
https://github.com/aldeed/meteor-collection2
https://github.com/aldeed/meteor-simple-schema
By using a schema you can define fields, which are calculated based on other fields, see the autoValue property: https://github.com/aldeed/meteor-collection2#autovalue
Then you can do something like this:
// Schema definition of User
{
...,
isVeryBusy: {
type: Boolean,
autoValue: function() {
return this.tasks.length > 5;
}
},
...
}
For all your basic questions, I can strongly recommend to read the DiscoverMeteor Book (https://www.discovermeteor.com/). You can read it in like 1-2 days and it will explain all those basic questions in a really comprehensible way.
Best Regards,

Answer 2

There is a very good package to implement the solution you are looking for. It is created by David Burles and it's called "meteor-collection-helper". Here it the atmosphere link:
You should check the link to see the examples presented there but according to the description you could implement some of the functionality you mentioned like this:
// Define the collections
Clients = new Mongo.Collection('clients');
Tasks = new Mongo.Collection('tasks');
// Define the Clients collection helpers
Clients.helpers({
isVeryBusy: function(){
return this.tasks.length > 5;
}
});
// Now we can call it either on the client or on the server
if (Meteor.isClient){
var client = Clients.findOne({_id: 123});
if ( client.isVeryBusy() ) runSomeCode();
}
// Of course you can use them inside a Meteor Method.
Meteor.methods({
addTaskToClient: function(id, task){
var client = Clients.findOne({_id: id});
if (!client.isVeryBusy()){
task._client = id;
Tasks.insert(task, function(err, _id){
Clients.update({_id: client._id}, { $addToSet: { tasks: _id } });
});
}
}
});
// You can also refer to other collections inside the helpers
Tasks.helpers({
client: function(){
return Clients.findOne({_id: this._client});
}
});
You can see that inside the helper the context is the document transformed with all the methods you provided. Since Collections are ussually available to both the client and the server, you can access this functionality everywhere.
I hope this helps.