CODEWITHSUNDEEP
meteormeteor-tracker
mc9
mc9

Reputation: 6341

Meteor tracker skips unexpectedly

I am following a tutorial about Tracker and seeing an unexpected behavior.

Here, I am using a getter and a setter to see that Tracker.autorun() is called whenever I call the setter.

if (Meteor.isClient) {
  var favoriteFood = 'Apples';
  var favoriteFoodDep = new Tracker.Dependency;

  var getFavoriteFood = function () {
    favoriteFoodDep.depend();
    return favoriteFood;
  };

  var setFavoriteFood = function (newValue) {
    favoriteFood = newValue;
    favoriteFoodDep.changed();
  };

  var handle = Tracker.autorun (function () {
    console.log("your favorite food is " + getFavoriteFood());
  });

  setFavoriteFood("Mangos");
  setFavoriteFood("Bananas");
  setFavoriteFood("Cheese");
}

When I open my browser console, I expect to see

Your favorite food is Apples
Your favorite food is Mangos
Your favorite food is Bananas
Your favorite food is Cheese

But All I see is the first and the last one, no matter how many calls I make for setFavoriteFood().

Your favorite food is Apples
Your favorite food is Cheese

Why is this happening?

Upvotes: 1

Views: 36

Answers (1)

e_m0ney
e_m0ney

Reputation: 980

I would guess that there is a race condition here. Because it executes the lines 

setFavoriteFood("Mangos");
setFavoriteFood("Bananas");
setFavoriteFood("Cheese");

.. so quickly, by the time the getter re-runs the invalidated computation, the set value is "Cheese".

To test this, consider running the following:

setFavoriteFood("Mangos");
window.setTimeout(function() { 
  setFavoriteFood("Bananas");
}, 1000);
window.setTimeout(function() { 
  setFavoriteFood("Cheese");
}, 2000);

I suspect that it will log all 4 to the console. Report back and let me know!

Upvotes: 1

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