如何等待 meteor.helper 中的计算，直到由于 template.autorun 中的依赖项更改而重新计算？

Question

当反应变量改变时我总是得到这个错误：

Exception in template helper: Error: $in needs an array
    at Error (native)
    at Object.ELEMENT_OPERATORS.$in.compileElementSelector (http://localhost:3000/packages/minimongo.js?cdf1a26cf7719fa9471a8017c3defd5aea812727:1827:15)
    at http://localhost:3000/packages/minimongo.js?cdf1a26cf7719fa9471a8017c3defd5aea812727:1509:19
    at Function._.each._.forEach (http://localhost:3000/packages/underscore.js?46eaedbdeb6e71c82af1b16f51c7da4127d6f285:157:22)
    at operatorBranchedMatcher (http://localhost:3000/packages/minimongo.js?cdf1a26cf7719fa9471a8017c3defd5aea812727:1489:5)
    at compileValueSelector (http://localhost:3000/packages/minimongo.js?cdf1a26cf7719fa9471a8017c3defd5aea812727:1393:12)
    at http://localhost:3000/packages/minimongo.js?cdf1a26cf7719fa9471a8017c3defd5aea812727:1372:9
    at Function._.each._.forEach (http://localhost:3000/packages/underscore.js?46eaedbdeb6e71c82af1b16f51c7da4127d6f285:157:22)
    at compileDocumentSelector (http://localhost:3000/packages/minimongo.js?cdf1a26cf7719fa9471a8017c3defd5aea812727:1355:5)
    at _.extend._compileSelector (http://localhost:3000/packages/minimongo.js?cdf1a26cf7719fa9471a8017c3defd5aea812727:1332:12)

我怀疑罪魁祸首是w（反应变量）

看看这个：

Template.cList.onCreated(function(){
  var self = this;
  self.d = new ReactiveVar()
  self.w = new ReactiveVar()
  self.autorun(function() {
    var b = A.findOne(Pi());
    if (b && b.array) {
      var h = Subs.subscribe('B', b.array)
      self.d.set(h.ready()) // is subscription ready?
      self.w.set(b.array)
    }
  });
});

Template.cList.helpers({
  cLists: function () {
    if (Template.instance().d.get() && Template.instance().w.get()) {  // run only when d and w is ready
      return B.find({_id: {$in:Template.instance().w.get()}}, {fields: {title:1, src:1}});
    }
  }
});

让我们一步步分解...

第一次没有错误
当我更改页面时，以下依赖项将更改：Pi()
Auto运行将重新运行.
因为Pi()改变，以下变量会改变：b && b.array && h && self.d.set(h.ready()) && self.w.set(b.array)
我怀疑 cList 是在页面更改后立即计算的，没有等待自动运行重新计算完成，这就是抛出错误的原因。
在自动运行完成重新计算依赖变化后，cLists根据依赖变化的变化显示正确的列表。用户界面确实没有问题。但是这个警告看起来很脏。

我想避免上面的警告是在依赖项更改时等待 cList。我怎么做？我如何等待 meteor.helper 中的计算，直到由于 template.autorun 中的依赖项更改而重新计算？

Answer 1

罪魁祸首是来自 meteorhacks:subs-manager 的 ready callback...用模板订阅更改它会避免错误...

Template.cList.onCreated(function(){
  var self = this;
  self.d = new ReactiveVar()
  self.w = new ReactiveVar()
  self.autorun(function() {
    var b = A.findOne(Pi());
    if (b && b.array) {
      self.subscribe('B', b.array)
      self.w.set(b.array)
    }
  });
});

Template.cList.helpers({
  cLists: function () {
    if (Template.instance().subscriptionsReady() && Template.instance().w.get()) {  // run only when subscription and w is ready
      return B.find({_id: {$in:Template.instance().w.get()}}, {fields: {title:1, src:1}});
    }
  }
});

如何等待 meteor.helper 中的计算，直到由于 template.autorun 中的依赖项更改而重新计算？

How to wait computation in meteor.helper until re-computation due to dependency change in template.autorun has been made?

javascript

meteor

meteor-helper

meteor-tracker