In Meteor, how to choose a collection based on a variable?

Question

Let's say you want to dynamically insert into different collections. Right now I am using a switch statement:

switch (i) {
  case "dog":
    Dog.insert({
      name: "Skippy"
    });
    break;
  case "cat":
    Cat.insert({
      name: "Skippy"
    });
    break;
}

But this is messy, and if I need to support future collections, it fails. Is there a way to choose the collection based on "i" in the example above?

soren468 · Accepted Answer · 2015-07-24T21:17:32.850

2

Correct me if I am wrong but I think this is what you are trying to do:

var Dog = {
  insert: function(props) {
    console.log(props);
  }
}

var insertArbitraryDocument = (function(collectionType, props) {
  window[collectionType].insert(props)
}).bind(this);

insertArbitraryDocument('Dog', {name: 'skippy'}); //=> {name: 'skippy'}

In this snippet you are accessing the window object and getting the property of whatever name you are passing in (must be exactly the same as the collection). Then you can call your usual function calls.

edited Jul 24 '15 at 21:17

answered Jul 24 '15 at 20:54

soren468

319
1
6

This is awesome. I didn't realize you can do `window[x]` to get to a variable x in the global scope. This is much better than what I proposed. – Christian Fritz Jul 24 '15 at 20:58
Thanks Christian. You can also do it on the server with `global[x]` – soren468 Jul 24 '15 at 21:03
1

I'd suggest using `this` instead of `window`. Then you can use the same code on server & client. – Matt K Jul 24 '15 at 21:11
This is great! I have a server function, so all I needed was `global[i].insert(...)`. Thanks! – Autumn Leonard Jul 24 '15 at 21:26

score 0 · Answer 2 · answered Jul 24 '15 at 20:47

I don't think there is a meteor built-in way of doing this, but it's pretty easy to just create a directory of collections manually:

JS in common to client and server:

var collections = {};

function myColl(name) {
    var coll = new Meteor.Collection(name);
    collections[name] = coll;
    return coll;
}

// and now just use myColl instead of new Meteor.Collection
Dog = myColl('dog');

And then, to do what you want to do:

collections[i].insert(data);

score 0 · Answer 3 · answered Jul 24 '15 at 21:22

Here's a complete working example:

Posts = new Mongo.Collection('posts');
Comments = new Mongo.Collection('comments');

var capitalize = function(string) {
  return string.charAt(0).toUpperCase() + string.slice(1);
};

var nameToCollection = function(name) {
  // pluralize and capitalize name, then find it on the global object
  // 'post' -> global['Posts'] (server)
  // 'post' -> window['Posts'] (client)
  var root = Meteor.isClient ? window : global;
  return root[capitalize(name) + 's'];
};

var insertSomething = function(name, data) {
  var collection = nameToCollection(name);
  collection.insert(data);
}

Meteor.startup(function() {
  // ensure all old documents are removed
  Posts.remove({});
  Comments.remove({});

  // insert some new documents
  insertSomething('post', {message: 'this a post'});
  insertSomething('comment', {message: 'this a comment'});

  // check that it worked
  console.log(Posts.findOne());
  console.log(Comments.findOne());  
});

Note this is nearly identical to this question but I simplified the answer for more generic use.

In Meteor, how to choose a collection based on a variable?

3 Answers3