Vulcan/packages/my-custom-package/lib/custom_fields.js

import Posts from "meteor/nova:posts";
import Users from 'meteor/nova:users';

/*
Let's assign a color to each post (why? cause we want to, that's why).
We'll do that by adding a custom field to the Posts collection.
Note that this requires our custom package to depend on nova:posts and nova:users.
*/

// check if user can create a new post
const canInsert = user => Users.canDo(user, "posts.new");
// check if user can edit a post
const canEdit = Users.canEdit;

const alwaysPublic = user => true;

Posts.addField(
  {
    fieldName: 'color',
    fieldSchema: {
      type: String,
      control: "select", // use a select form control
      optional: true, // this field is not required
      insertableIf: canInsert,
      editableIf: canEdit,
      viewableIf: alwaysPublic,
      form: {
        options: function () { // options for the select form control
          return [
            {value: "white", label: "White"},
            {value: "yellow", label: "Yellow"},
            {value: "blue", label: "Blue"},
            {value: "red", label: "Red"},
            {value: "green", label: "Green"}
          ];
        }
      },
      publish: true // make that field public and send it to the client
    }
  }
);

/*
The main post list view uses a special object to determine which fields to publish,
so we also add our new field to that object:
*/

import PublicationUtils from 'meteor/utilities:smart-publications';

PublicationUtils.addToFields(Posts.publishedFields.list, ["color"]);