what is the difference of subscribing collection under waitOn , subscriptions and onBeforeAction

Question

I would like to the difference if any in the following ways of subscribing data,

using waitOn

waitOn:function(){
  Meteor.subscribe('//some published function)
 }

using onBeforeAction

Router.onBeforeAction : function(){
   Meteor.subscribe('//some published function)
 }

using subscriptions

subscriptions: function() {
    this.subscribe('items');
   }

Answer 1

If you want to publish data only for authorized users, it is possible that you check (if user is authenticated) for a route, in onBeforeAction. Something like:

Router.map(function(){

  this.route('home', {
    path : '/',
    template : 'home'
  });

  this.route('register', {
    path : '/register',
    template : 'register'
  });

  this.route('login', {
    path : '/login',
    template : 'login'
  });

  this.route('requestlisting', {
    path : '/requestlisting',
    template : 'requestlisting',
    waitOn : function(){
        return Meteor.subscribe('RequestsPublication');
    }
  });
  ...
});

var requireLogin = function () {
   if(!Meteor.user()){
       if(Meteor.loggingIn()){
          this.render(this.loadingTemplate);
       }else{
          Router.go('login');
       }
   } else {
       this.next();
   }
}

Router.onBeforeAction(requireLogin, {only: ['requestlisting',...]});

In this example, in onBeforeAction, routing occurs for 'requestlisting' only if a user logged in, after then it makes sense to subscribe to any data.