Iron Router data fires 3 times

Question

I have this route set up with a loding template on Router.Config

Router.onBeforeAction('loading');
this.route('clients', {
    path: '/clients',
    template: 'clientsAll',
    waitOn: function () {
        return Meteor.subscribe('clientsAll');
    },
    data: function () {
        if (this.ready()) {
            console.log("Data");
            return Clients.find().fetch();
        }
    }
});

Everything works fine it displays the loading template before rendering the template, but on the log it shows data being fired twice.

Answer 1

This is a normal behavior, data like most route methods is run inside a reactive computation.

In your data method you depend on this.ready() which happens to be a reactive data source (it returns the state of the wait list returned by waitOn).

So basically this is what is going on :

• your data method is declared as a computation and initially runs with this.ready() returning false.
• the subscription you wait on becomes ready some time in the future so this.ready() now returns true and your data method is rerun.

This is not a problem because data methods are usually not computational heavy (they just return some data that is available locally on the client).