Meteor Collection转换：它是在服务器上还是在客户端上完成的？或者取决于 [英] Meteor Collection Transform: is it done on the server or on the client? or it depends

问题描述

我想使用transform从集合中创建一个虚拟字段。但是，我添加的新字段（在转换函数中）正在向返回的文档添加相当多的数据。

I want to use transform to make a "virtual field" out of a collection. However, the new field I'm adding (within the transform function) is adding quite a bit of data to the returned document.

如果转换发生在客户端内，这很好。如果在服务器端完成，则会出现带宽问题。

This is fine if the transform is taking place inside the client. If it is done on server-side, then there will be bandwidth concerns.

所以我想知道转换是在服务器上还是在客户端上完成的，或者取决于我如何查找/获取文档？

So I'm wondering if the transform is done on the server, or on the client, or it depends on how I find/fetch the document?

推荐答案

更新：可以这样做服务器上的转换。

UPDATE: It's possible to do a transform on the server.

您可以在客户端进行如下转换：

You can have a transform on the client like this:

return YourCollection.find({}, {transform: function (doc) {
   doc.test = true;
   return true;
}});

Meteor忽略转换对已发布的查询（来自 Meteor.publish ）。客户端看到文档就好像转换不存在一样。

Meteor ignores transform on queries that are published (from within Meteor.publish). The client sees the document as if the transform didn't exist.

如果您想在服务器上使用转换，您可以这样做：

If you would like to use transforms on the server you can do this:

YourCollection = new Mongo.Collection("collection_name"); 

Meteor.publish("yourRecordSet", function() {

  //Transform function
  var transform = function(doc) {
    doc.date = new Date();
    return doc;
  }

  var self = this;

  var observer = YourCollection.find().observe({
      added: function (document) {
      self.added('collection_name', document._id, transform(document));
    },
    changed: function (newDocument, oldDocument) {
      self.changed('collection_name', newDocument._id, transform(newDocument));
    },
    removed: function (oldDocument) {
      self.removed('collection_name', oldDocument._id);
    }
  });

  self.onStop(function () {
    observer.stop();
  });

  self.ready();

});

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