我该如何保持出版物的反应？

Question

I am migrating from a custom user rights management system to Alanning:roles v2.0 . I have a very basic structure:

• A basic user
• Groups of users, each with specific settings. I store them in a "group" collection.
• A group admin status for users who manage the groups (each group has its group admins).

I was previously storing the group members and admins mongo _id in the "group" document. This way, I could publish the groups reactively : I just had to check if the userId was in the group document, in the "members" or "admins" fields.

Now that I switched to a right management enforced by Alanning:roles, I do something like this in my publication :

const userGroupsAsAdmin = Roles.getPartitionsForUser (this.userId, ['group_admin'])
const userGroupsAsMember = Roles.getPartitionsForUser (this.userId, ['member'])
const selector = {$or:[{'_id':{$in: userGroupsAsMember}},{'_id':{$in: userGroupsAsAdmin}}]}
const options = {}
const response = Groups.find(selector, options)
return response

Note that Roles.getPartitionsForUser () is just the new function name for Roles.getGroupsForUser () .

The problem here is that the publication don't watch for changes in the role collection, so when a user becomes member, the publication isn't updated. I know this is a common issue and I know 3 ways to fix this, but none of them feels satisfying:

• The best candidate: denormalize and duplicate. I keep my members and admins fields in the group document. What bugs me is that I will keep 2 versions of the same thing and create a possibility for inconsistencies to appear.

• Add an argument to the publication and rerun it using this argument (eg userGroupsAsMember ) but it relies on client and makes it send unnecessary info.

• Use low level publication api, either directly or using a package . I already did this directly in the past but I don't want to rely on Cursor.observe() anymore because it doesn't scale efficiently and create an unnecessary server load.

Am I missing an option? If not, what would be the best way to keep my publication reactive?

Answer 1

Use reywood:publish-composite to create a reactive join.

Meteor.publishComposite("my-groups", {
  find: function() {
      // findOne won't work, it's not a cursor
      return Meteor.users.find(
        {_id: this.userId},
        {fields: {roles: 1}}
      );
    },
  children: [{
    find: function(user) {
      // getPartitionsForUser allows the first parameter to be the actual user object.
      const userGroupsAsAdmin = Roles.getPartitionsForUser (user, ['group_admin']);
      const userGroupsAsMember = Roles.getPartitionsForUser (user, ['member']);
      const selector = {$or:[{'_id':{$in: userGroupsAsMember}},{'_id':{$in: userGroupsAsAdmin}}]};
      const options = {};
      const response = Groups.find(selector, options);
      return response;
    }
  }]
});

Roles.getPartitionsForUser doesn't return a cursor, therefore it can't be reactive. That's why you'll need to publish a Meteor.users.find call, too.