How do Meteor.userId(), this.userId, and Meteor.user() work internally?

merlinpatt · August 16, 2016, 1:52am

Can someone either explain the internals of how each of these work or point me to the implemented code?

Meteor.userId()
this.userId
Meteor.user()

Also, what does the this in this.userId refer to?

Edit: Clarified that I want to know the internals of how these work, not what they do.

khamoud · August 16, 2016, 3:11am

Meteor.user() - Get the current user record, or null if no user is logged in. A reactive data source.
Meteor.userId() - Get the current user id, or null if no user is logged in. A reactive data source.
this.userId - Access inside the publish function. The id of the logged-in user, or null if no user is logged in. and The id of the user that made this method call, or null if no user was logged in.

merlinpatt · August 16, 2016, 4:26am

Apologies, I should have clarified better. I understand what they do. I want to know how they do it.

Does Meteor.user() call use Meteor.userId() in its function or is it the other way around?
Or are they independent of each other?
What about this.userId and what this refers to?

khamoud · August 16, 2016, 4:50am

Ah I see.

Meteor.user() calls Accounts.user() which is found here:

github.com

meteor/meteor/blob/master/packages/accounts-base/accounts_common.js#L245


      DEFAULT_PASSWORD_ENROLL_TOKEN_EXPIRATION_DAYS) * 24 * 60 * 60 * 1000;
}


_tokenExpiration(when) {
  // We pass when through the Date constructor for backwards compatibility;
  // `when` used to be a number.
  return new Date((new Date(when)).getTime() + this._getTokenLifetimeMs());
}


_tokenExpiresSoon(when) {
  var minLifetimeMs = .1 * this._getTokenLifetimeMs();
  var minLifetimeCapMs = MIN_TOKEN_LIFETIME_CAP_SECS * 1000;
  if (minLifetimeMs > minLifetimeCapMs)
    minLifetimeMs = minLifetimeCapMs;
  return new Date() > (new Date(when) - minLifetimeMs);
}
}


var Ap = AccountsCommon.prototype;


// Note that Accounts is defined separately in accounts_client.js and

Meteor.userId() calls Accounts.userId() which is found here:

github.com

meteor/meteor/blob/master/packages/accounts-base/accounts_common.js#L236


}


_getPasswordResetTokenLifetimeMs() {
  return (this._options.passwordResetTokenExpirationInDays ||
          DEFAULT_PASSWORD_RESET_TOKEN_EXPIRATION_DAYS) * 24 * 60 * 60 * 1000;
}


_getPasswordEnrollTokenLifetimeMs() {
  return (this._options.passwordEnrollTokenExpirationInDays ||
      DEFAULT_PASSWORD_ENROLL_TOKEN_EXPIRATION_DAYS) * 24 * 60 * 60 * 1000;
}


_tokenExpiration(when) {
  // We pass when through the Date constructor for backwards compatibility;
  // `when` used to be a number.
  return new Date((new Date(when)).getTime() + this._getTokenLifetimeMs());
}


_tokenExpiresSoon(when) {
  var minLifetimeMs = .1 * this._getTokenLifetimeMs();
  var minLifetimeCapMs = MIN_TOKEN_LIFETIME_CAP_SECS * 1000;

Accounts.user() is implemented here:

github.com

meteor/meteor/blob/master/packages/accounts-base/accounts_common.js#L57


 * @locus Anywhere
 */
userId() {
  throw new Error("userId method not implemented");
}


/**
 * @summary Get the current user record, or `null` if no user is logged in. A reactive data source.
 * @locus Anywhere
 */
user() {
  var userId = this.userId();
  return userId ? this.users.findOne(userId) : null;
}


// Set up config for the accounts system. Call this on both the client
// and the server.
//
// Note that this method gets overridden on AccountsServer.prototype, but
// the overriding method calls the overridden method.
//

Accounts.userId() is implemented here:

github.com

meteor/meteor/blob/master/packages/accounts-base/accounts_common.js#L49


  this._onLogoutHook = new Hook({
    bindEnvironment: false,
    debugPrintExceptions: "onLogout callback"
  });
}


/**
 * @summary Get the current user id, or `null` if no user is logged in. A reactive data source.
 * @locus Anywhere
 */
userId() {
  throw new Error("userId method not implemented");
}


/**
 * @summary Get the current user record, or `null` if no user is logged in. A reactive data source.
 * @locus Anywhere
 */
user() {
  var userId = this.userId();
  return userId ? this.users.findOne(userId) : null;

this.userId for methods is implemented here:

github.com

meteor/meteor/blob/master/packages/ddp-common/method_invocation.js#L38


 */
this.isSimulation = options.isSimulation;


// call this function to allow other method invocations (from the
// same client) to continue running without waiting for this one to
// complete.
this._unblock = options.unblock || function () {};
this._calledUnblock = false;


// current user id


/**
 * @summary The id of the user that made this method call, or `null` if no user was logged in.
 * @locus Anywhere
 * @name  userId
 * @memberOf DDPCommon.MethodInvocation
 * @instance
 */
this.userId = options.userId;


// sets current user id in all appropriate server contexts and

this.userId for publications is implemented here:

github.com

meteor/meteor/blob/master/packages/ddp-server/livedata_server.js#L988




// Only named subscriptions have IDs, but we need some sort of string
// internally to keep track of all subscriptions inside
// SessionDocumentViews. We use this subscriptionHandle for that.
if (self._subscriptionId) {
  self._subscriptionHandle = 'N' + self._subscriptionId;
} else {
  self._subscriptionHandle = 'U' + Random.id();
}


// has _deactivate been called?
self._deactivated = false;


// stop callbacks to g/c this sub.  called w/ zero arguments.
self._stopCallbacks = [];


// the set of (collection, documentid) that this subscription has
// an opinion about
self._documents = {};


// remember if we are ready.

this with regards to a publication is a Subscription object which is implemented here:

github.com

meteor/meteor/blob/master/packages/ddp-server/livedata_server.js#L937


  // the original IP address of the client connecting to the first
  // proxy.  However, the end user can easily spoof the header, in
  // which case the first value(s) will be the fake IP address from
  // the user pretending to be a proxy reporting the original IP
  // address value.  By counting HTTP_FORWARDED_COUNT back from the
  // end of the list, we ensure that we get the IP address being
  // reported by *our* first proxy.


  if (httpForwardedCount < 0 || httpForwardedCount > forwardedFor.length)
    return null;


  return forwardedFor[forwardedFor.length - httpForwardedCount];
}
});


/******************************************************************************/
/* Subscription                                                               */
/******************************************************************************/


// ctor for a sub handle: the input to each publish function

this with regards to a method is a DDPCommon.MethodInvocation which is implemented here:

github.com

meteor/meteor/blob/master/packages/ddp-common/method_invocation.js#L9


// Instance name is this because it is usually referred to as this inside a
// method definition
/**
* @summary The state for a single invocation of a method, referenced by this
* inside a method definition.
* @param {Object} options
* @instanceName this
* @showInstanceName true
*/
DDPCommon.MethodInvocation = function (options) {
 var self = this;


 // true if we're running not the actual method, but a stub (that is,
 // if we're on a client (which may be a browser, or in the future a
 // server connecting to another server) and presently running a
 // simulation of a server-side method for latency compensation
 // purposes). not currently true except in a client such as a browser,
 // since there's usually no point in running stubs unless you have a
 // zero-latency connection to the user.

merlinpatt · August 16, 2016, 1:42pm

This is something I don’t get. How does userId() return the current userId if its implementation is to throw an error?

hwillson · August 16, 2016, 2:14pm

The AccountsCommon class contains a userId() function as a placeholder only (an abstract function or method). In the same accounts-base package, you’ll see that both AccountsClient and AccountsServer extend AccountsCommon, and override the userId() function with their own versions. These are the versions that you actually end up calling. You can see the full details in:

github.com

meteor/meteor/blob/f9f94e21d10676aaa4a8a6809cb3bbc2fa60f536/packages/accounts-base/accounts_client.js#L38-L40


userId() {
  return this.connection.userId();
}

github.com

meteor/meteor/blob/f9f94e21d10676aaa4a8a6809cb3bbc2fa60f536/packages/accounts-base/accounts_server.js#L69-L84


// @override of "abstract" non-implementation in accounts_common.js
userId() {
  // This function only works if called inside a method. In theory, it
  // could also be called from publish statements, since they also
  // have a userId associated with them. However, given that publish
  // functions aren't reactive, using any of the infomation from
  // Meteor.user() in a publish function will always use the value
  // from when the function first runs. This is likely not what the
  // user expects. The way to make this work in a publish is to do
  // Meteor.find(this.userId).observe and recompute when the user
  // record changes.
  var currentInvocation = DDP._CurrentInvocation.get();
  if (!currentInvocation)
    throw new Error("Meteor.userId can only be invoked in method calls. Use this.userId in publish functions.");
  return currentInvocation.userId;
}