How to use when - 10 common examples

'NotOrdered': function NotOrdered(event, commit, deps){
			if(event.eventType === 'OrderPlaced'){
				// Start packaging the order from which the event came.
				return deps.startPackaging(commit.sequenceID).then(function(){
					return when.resolve(new Event('OrderPlaced', {
						orderID: commit.sequenceID
					}));
				});
			}
			else{
				return when.reject();
			}
		},
		'Ordered': function Ordered(event, commit, deps){

// node modules
var fs = require('fs');
var os = require('os');
var path = require('path');

// 3rd party modules
var execa = require('execa');
var when = require('when');
var whenNode = require('when/node');

// implementation
var mkdir = whenNode.lift(fs.mkdir);
var readFile = whenNode.lift(fs.readFile);
var rimraf = whenNode.lift(require('rimraf'));

// public
module.exports = {
  setNpmVersion: function (npmVersion) {
    return execa('npm', ['install', '-g', 'npm@' + npmVersion]);
  },
  getNpmVersion: function () {
    return execa.stdout('npm', ['-v']);
  },
  createTestApp: function (dirPath, packagePath) {
    return mkdir(dirPath).then(function () {
      return when.promise(function (res, rej) {
        var read = fs.createReadStream(packagePath);
        var write = fs.createWriteStream(path.join(dirPath, 'package.json'));

return when.try(self._eventSink.sink.bind(self._eventSink), commitObject).then(function _commitSinkSucceeded(result) {
		// Now that the commit is sunk, we can clear the event staging area - new events will end up in subsequent commits.
		self._stagedEvents = [];
		self._updateSequenceNumber(commitObject.sequenceSlot);
		//NOTE: The check/log emission below is a good candidate for refactoring into Aspect-Oriented Programming.
		// ESDF Core does not support AOP as of now, though.
		if(self._IOObserver){
			self._IOObserver.emit('CommitSinkSuccess', {
				commitObject: commitObject
			});
		}
		// Now that the commit has been saved, we proceed to save a snapshot if the snapshotting strategy tells us to (and we have a snapshot save provider).
		//  Note that _snapshotStrategy is called with "this" set to the current aggregate, which makes it behave like a private method.
		if (self.supportsSnapshotGeneration() && self._snapshotter && self._snapshotStrategy && self._snapshotStrategy(commitObject)) {
			when.try(self._saveSnapshot.bind(self)).catch(function(error) {
				//TODO: We should not be using console directly, but there is currently
				// no way to inject a custom logger.
				console.error('Error saving snapshot for %s [%s]: %s', self._aggregateID, self._aggregateType, error);
			});
			// Since saving a snapshot is never mandatory for correct operation of an event-sourced application, we do not have to react to errors.
		}
		return result;
	}, function _commitSinkFailed(reason) {
		// Sink failed - do nothing. An upper layer can either retry the sinking, or reload the aggregate and retry (in the latter case, the sequence number will probably get refreshed).

bootstrap: function(argv) {
    var projectRootDir = getProjectRootDir();
    if (projectRootDir !== null) {
      console.log(chalk.red('Initialization Error') + ' - Can\'t create new firebase app ' +
        'inside an existing firebase project');
      process.exit(1);
    }
    _when.join(this.getTemplates(), auth.listFirebases(argv)).done(function(resultSet) {
      var supportedTemplates = resultSet[0],
          res = resultSet[1];

      if (res.firebases.length === 0) {
        console.log(chalk.yellow('You have no apps in your Firebase account'));
        console.log('Sign in to %s and create an app', chalk.cyan('https://firebase.com'));
        console.log('then initialize a directory for hosting');
        process.exit(1);
      }

      // Firebase names always a subset of ^[0-9a-z-]*$ so safe to regex
      var templateList = Object.keys(supportedTemplates).sort();
      var firebasePattern = new RegExp('^(' + res.firebases.join('|') + ')$');
      var templatePattern = new RegExp('^(' + templateList.join('|') + ')$');
      if (!argv.firebase || (typeof(argv.firebase) !== 'string') || !argv.firebase.match(firebasePattern)) {
        res.showFirebases();

add : function(props) {

    var self = this;
    var def = when.defer();
    var checkExistance = when.defer();
    var tagDef = when.defer();

    try {

      // if we have an original url, make sure it's a url
      if (props.original_url && props.original_url.length) {
        assert(Validator.isURL(props.original_url), "original_url isn't a URL");

        // check if this already exists, based on URL. if it does, exit.
        self.forge({ original_url : props.original_url }).fetch().then(function(submission) {
          console.log(submission);
          if (typeof submission !== "undefined" && submission !== null) {
            checkExistance.reject("This example already exists. Id " + submission.id);
          } else {
            checkExistance.resolve();
          }
        });

} catch (err) {
        service.logger.error('Post Start Init Service Error:', err);
        return when.reject(err);
      }
    }

    //
    result = service.resources.postStartInit();
    service._promiseQueue.push(result);

    // wait for Q'd resources to resolve before letting service resolve
    if (service._promiseQueue.length) {
      service.logger.info('Wait Post Start Init...');

      // TODO: need timeout in case resource promise never resolves
      return when.all(service._promiseQueue).then(function () {
        delete service._promiseQueue;

        service.logger.info('Loaded');
        service.logger.groupEnd(' ');
      });
    } else {
      service.logger.groupEnd(' ');

      return 1;
    }
  }.bind(this)).then(function (result) {
    logger.groupEnd('Done Running All Post Start Inits');

.then(webhooks => {

        // remove all webhooks on stop
        if(!flint.options.removeWebhooksOnStart) {
          var webhooksToRemove = _.filter(webhooks, webhook => {
            return (webhook.name == u.base64encode(flint.options.webhookUrl.split('/')[2] + ' ' + flint.email));
          });

          if(webhooksToRemove instanceof Array && webhooksToRemove.length > 0) {
            return when.map(webhooksToRemove, webhook => flint.spark.webhookRemove(webhook.id))
              .then(() => when(true))
              .catch(() => when(true));
          } else {
            return when(true);
          }
        }

        // else, only remove webhooks this app created
        else {
          return when.map(webhooks, webhook => flint.spark.webhookRemove(webhook.id))
            .then(() => when(true))
            .catch(() => when(true));
        }

      });
  } else {

return when.promise(function(resolve,reject) {
                var promises = [];
                
                whenNode.call(fs.readdir,dir).done(function(files) {
                    files = files.sort();
                    files.forEach(function(fn) {
                        var stats = fs.statSync(path.join(dir,fn));
                        if (stats.isFile()) {
                            if (/\.js$/.test(fn)) {
                                promises.push(when.promise(function(resolve,reject) {
                                    loadNode(dir,fn).then(resolve, function(err) {
                                        resolve({'fn':fn,err:err});
                                    });
                                }));
                            }
                        } else if (stats.isDirectory()) {
                            // Ignore /.dirs/, /lib/ /node_modules/ 
                            if (!/^(\..*|lib|icons|node_modules|test)$/.test(fn)) {
                                promises.push(when.promise(function(resolve,reject) {
                                    loadNodes(path.join(dir,fn)).then(function(errs) {

readable._read = function _read(length) {
			var self = this;
			when.try(reader, sequenceID, currentOffset).then(function(commits) {
				if (!Array.isArray(commits) && commits !== null) {
					throw new Error('Expected an array of Commit objects, but got an unknown type from the commit reader function');
				}
				// Move forward in the stream:
				if (Array.isArray(commits)) {
					currentOffset += commits.length;
				}
				// Only perform one push(). Multiple pushes from one _read() are apparently a sure-fire way to cause a huge memory leak.
				self.push(commits);
			}).catch(function(error) {
				self.emit('error', error);
			});
		};
	}

}).then(function runUserFunction(loadingResult) {
			var aggregateInstance = loadingResult.instance;
			var stagedCommit;

			return when.try(userFunction, aggregateInstance).then(function saveAggregateState(userFunctionResult) {
				// Get the events staged by the aggregate root in course of execution and eventually append them to the result if requested.
				try {
					stagedCommit = aggregateInstance.getCommit(options.commitMetadata || {});
				} catch (commitConstructionError) {
					// no-op: we've failed to construct the commit; maybe the aggregate
					//  root instance has no ID assigned? Anyway, commit() will either
					//  fail or succeed without writing anything (0 events). This is not
					//  a common case, but a useful one when loading "dummy entities"
					//  which are guaranteed to be in their initial state. This also
					//  ensures compatibility with esdf 0.1.x.
				}

				// Actually commit:
				return when.try(aggregateInstance.commit.bind(aggregateInstance), options.commitMetadata || {}).then(function _buildOutput() {
					// If the caller has requested an "advanced format" result, pass the data through to them, enriched with the result of the user function.
					if (options.advanced) {