Convert async.waterfall to Bacon

Question

I'm trying to integrate Baconjs into my current Nodejs project, in this project I used Async https://github.com/caolan/async to handle callbacks. One of the methods is async.waterfall that is now I want to port it to Bacon, using Bacon.fromNodeCallback(...). My code in NodeJS:

async.waterfall([
  function findCondition(callback) {
    conditionBoundary.findById(condition.id, callback);
  },

  function updateCondition(loadedCondition, callback) {
     if(loadedCondition) {
      condition.created = loadedCondition.created;

      conditionBoundary.updateCondition(condition, function(error, numberOfDocs) {
        if(error) {
          return callback(error);
        }

        if(loadedCondition.prettyUrl && loadedCondition.prettyUrl !== condition.prettyUrl) {
          return callback(null, true, loadedCondition);
        }

        callback(null, false, null);
      });
    }
  },

  function updateLinkInConditionDescription(isUpdated, loadedCondition, callback) {
    if(isUpdated) {

      conditionBoundary.findByPrettyUrlInDescription(loadedCondition.prettyUrl, function(error, docs) {
        if(error) {
          return callback(null, false);
        }

        async.each(docs, function(doc, eachCallback) {
          var desc = doc.vietnamese.description;
          desc = desc.replace(new RegExp(loadedCondition.prettyUrl, "gmi"), condition.prettyUrl);

          conditionBoundary.updateVietnameseDescription(doc.id, desc, eachCallback);
        }, function(error) {
          callback(null, false);
        });
      });
    } else {
      return callback(null, true);
    }
  }
], function(error, result) {
  if(error) {
    return done(false, util.error("Failed to update condition")("system"));
  }

  done(true, { message: "Condition has been updated" });
});

So I did it this way:

var result1 = Bacon.fromNodeCallback(fn, params...);
result1.onValue(function(val) {
  // perform some logic

  var result2 = Bacon.fromNodeCallback(fn2, params...);
  result2.onValue(function(val)) { .... }

  // and so on...
});

I feel like Im not doing it right. So what is the right way the accomplish this? I just get my head around with Bacon so any help can be really appreciated. Thanks!

You should probably add the original code using async, it might help to see what you're trying to accomplish. — Kevin Sandow, Jul 25 '14 at 06:38
+1 for the title :D Sounds like transforming water to wine :D — Zarathustra, Jul 25 '14 at 09:08

score 0 · Accepted Answer · answered Jul 28 '14 at 03:02

Well, I finally solve my own problem after googling and reading this article http://abesto.net/bacon-js-on-the-server/. It makes me think about my problem and what I need to do with Bacon to archive the goal, rather then focus on converting async.waterfall method to Bacon. So I post my code here, hope that someone finds it useful:

var oldConditionStream = Bacon.fromNodeCallback(conditionBoundary,
                                                "findById",
                                                info.id).flatMap(function(oldCondition) {
  if(oldCondition) {
    return Bacon.once(oldCondition);
  } else {
    return Bacon.once(new Bacon.Error("fail"));
  }
});

oldConditionStream.onError(function(error) {
  return done(false, { message: "Failed to update condition" });
});

var updatingStream = oldConditionStream.flatMap(function(oldCondition) {
  condition.created = util.parseDate(oldCondition.created, "YYYY-MM-DD h:mm:ss a");

  return Bacon.fromNodeCallback(conditionBoundary, "updateCondition", condition).flatMap(function(nod) {
    if(!nod) {
      return Bacon.once(new Bacon.Error("fail"));
    }

    return Bacon.once(oldCondition);
  });
});

updatingStream.onError(function(error) {
  return done(false, util.error("Failed to update condition")("system"));
});
var updatingDescriptionStream = updatingStream.flatMap(function(oldCondition) {
  if(!_.isEqual(oldCondition.prettyUrl, condition.prettyUrl)) {
    var findingStream = Bacon.fromNodeCallback(conditionBoundary,
                                                    "findByPrettyUrlInDescription",
                                                    oldCondition.prettyUrl).flatMap(Bacon.fromArray);
    var anotherStream = findingStream.flatMap(function(cond) {
      var desc = cond.vietnamese.description;
      desc = desc.replace(new RegExp(oldCondition.prettyUrl, "gmi"), condition.prettyUrl);
      return Bacon.fromNodeCallback(conditionBoundary, "updateVietnameseDescription", cond.id, desc).map(true);
    });

    anotherStream.onEnd(function() {
      return Bacon.once(true);
    });

  } else {
    return Bacon.once(true);
  }
});

updatingDescriptionStream.onValue(function(flag) {
  return done(true, { message: "Condition has been updated" });
});

Cheer!

Convert async.waterfall to Bacon

1 Answers1