使 Meteor 对 Meteor.user() 的特定子项具有反应性 [英] Make Meteor Reactive to Specific Subitem of Meteor.user()

问题描述

我需要使用一些存储在用户 Meteor.user() 对象中的子属性，例如 Meteor.user().profile.preferences.preference_one，Meteor.user().profile.preferences.preference_two 等等.这些子属性被用在反应式自动运行块中，因为在它们发生变化时必须进行重新计算.

I need to use some subproperties which are stored in the user's Meteor.user() object, such as Meteor.user().profile.preferences.preference_one, Meteor.user().profile.preferences.preference_two, et cetera. These subproperties are being used inside reactive autorun blocks because there are recalculations that must be done anytime they change.

我发现当我从一个反应块中引用这些子属性的值时，自动运行会被触发以任何对Meteor.user() 对象，包括不会以任何方式影响我明确引用的数据的更改.例如，如果 Meteor.user().profile.name 已更新，则任何包含 Meteor.user().profile.preferences.preference_one 或 的自动运行Meteor.user().profile.preferences.preference_two 也会被触发，因为它们都有一个共同的父级.

I've discovered that when I refer to the value of these subproperties from within a reactive block, then the autorun is fired for any change to the Meteor.user() object, including changes which do not affect in any way the data that I am explicitly referencing. For example, if Meteor.user().profile.name is updated, then any autorun that includes Meteor.user().profile.preferences.preference_one or Meteor.user().profile.preferences.preference_two gets fired as well, because they all have a common parent.

我看过一个类似的问题 处理限制 Meteor 反应性的范围，但它处理自定义集合，而不是 Meteor.users 集合.我看不到那里的解决方案如何适用，因为他们在订阅中指定字段以限制发布到客户端的子属性，在我的情况下，我需要 Meteor.user().但我需要能够选择我对哪些子属性做出反应！

I have seen a similar question dealing with limiting the scope of Meteor's reactivity, but it deals with a custom collection, not the Meteor.users collection. I cannot see how the solution there could be made applicable because they are specifying fields in subscriptions to limit what subproperties are published to the client, and in my case, I need all the subproperties of Meteor.user(). But I need to be able to choose which subproperties I am reacting to!

在本地存储子属性值，然后比较每个更改当然可以工作，但这是一个蛮力解决方案，因为它需要额外的逻辑并且自动运行无论如何都会被触发.

Storing subproperty values locally and then comparing on every change would of course work, but it is a brute force solution solution in that it requires extra logic and that the autoruns will all be firing anyway.

推荐答案

我不知道这是否是最佳方式，但看看这个例子:

I don't know if this is the best way, but have a look at this example:

Tracker.autorun(function() {
  var user = Meteor.user();
  if (user && user.profile)
    Session.set('p1', user.profile.preference1);
});

Tracker.autorun(function() {
  var p1 = Session.get('p1');
  console.log("p1 is " + p1);
});

第一个 autorun 将在每次用户数据更改时触发，但是第二个 autorun 仅在特定属性更改时触发.

The first autorun will fire every time the user data changes, however the second autorun will fire only when that particular property changes.

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