javascript - meteor ReactiveVar - TypeError : Cannot call method 'set' of undefined

Question

我尝试使用 ReactiveVar。我不知道如何处理 ReactiveVar。这是我试过的代码。

Template.Home.helpers({
  names: function(){
    temp = Template.instance().name.get();
    return temp;
  }
});

Template.Home.onCreated(function () {
  this.name = new ReactiveVar();
  Meteor.call("getNames", function(error, result) {
    if(error){
      alert("Oops!!! Something went wrong!");
      return;
    } else {
      this.name.set(result); // TypeError: Cannot call method 'set' of undefined
      return;
    }
  });
});

我设置和获取 ReactiveVar 是否正确？或者如何设置和获取 ReactiveVar ??

Answer 1

你的逻辑是正确的，你的错误实际上是一个常见的 JS 陷阱:在 Meteor.call 回调函数内部，修改了 this 范围，不再引用模板实例.

您需要使用 Function.prototype.bind 并更新您的代码:

Template.Home.onCreated(function () {
  this.name = new ReactiveVar();
  Meteor.call("getNames", function(error, result) {
    if(error){
      alert("Oops!!! Something went wrong!");
      return;
    }
    this.name.set(result);
  // bind the template instance to the callback `this` context
  }.bind(this));
});

你也可以使用闭包捕获的局部变量(你会经常在 JS 项目中看到这种风格):

Template.Home.onCreated(function () {
  // use an alias to `this` to avoid scope modification shadowing
  var template = this;
  template.name = new ReactiveVar();
  // the callback is going to capture the parent local context
  // it will include our `template` var
  Meteor.call("getNames", function(error, result) {
    if(error){
      alert("Oops!!! Something went wrong!");
      return;
    }
    template.name.set(result);
  });
});