Meteor.js: How to avoid useless refresh/computation/re-render with dot notation
Question
I'm needing a way to avoid useless computations; In reactive functions, I have a reactive object, I just need one property, but if one other of this object change, all the function is recalculated:
Template.registerHelper('name', function() {
console.log("running");
return Meteor.user().profile.name;
});
(In html
<body><p>My name: {{name}}</p></body>
)
Now let change your age:
Meteor.users.update({_id:Meteor.userId()},{$set:{"profile.age":20}});
You guess what you see in your console(for the second time...)
running x2
but it should run only once because the name haven't changed
Why it's important ? In my application I have complex calculs, and user online/idle status is changing easily
1 answers
solution1
1 ACCPTED 2016-04-14 00:46:38
The computation is rerun whenever the value of used reactive function changes. In your case, the reactive function is Meteor.user() , so whenever result of that method changes, rerun is triggered.
To limit reruns to where it's really necessary, you need to use (or create) a reactive function that will return exactly the value you want to track and nothing more. For example:
var prop = new ReactiveVar();
Template.template.onRendered(function() {
this.autorun(function() {
prop.set(Meteor.user().profile.name);
});
});
Template.template.helpers({
hlpr: function() {
console.log("RERUN!!!");
return prop.get();
},
});
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