How to optimize this Node.js + q code to prevent callback hell? -



How to optimize this Node.js + q code to prevent callback hell? -

i using q prevent callback hell have reached part of code don't know how arrange:

i searching scheduled messages delivered. each of them, seek send them 1 1 , if sent, removes database. ugly part have then() within loop. way end having nested promises instead of nested callbacks!!!! suggestions?

applog.debug("looking scheduled messages"); var messages = messageservice.findscheduled() .then(function(messages){ applog.debug("found [%d] stored messages",messages.length); for(var = 0; i<messages.length; i++){ messageservice.send(msg.namespace, msg.message, msg.data) .then(function(result) { if (result == constants.event_emit_sent) { applog.debug("message [%s] sent!!!", msg._id); messageservice.remove(msg._id) .then(function(result) { applog.debug("message deleted: [%s]", msg._id); }) .fail(function(err) { applog.error("the message couldn't deleted: [%s]", msg._id); }); }else if (result == constants.event_emit_not_sent_and_not_stored) { applog.debug("message [%s] not sent", msg._id); } }); } });

the ugly part have then() within loop

no, can happen. though functional programming style of promises leads using .map() callback anyway :-) looping command structure, , require nesting (except use exceptions command flow, i.e. branching). don't have nest promises in promise callbacks, though.

i'd simplify loop body to

function sendanddelete(msg) { homecoming messageservice.send(msg.namespace, msg.message, msg.data) .then(function(result) { if (result == constants.event_emit_sent) { applog.debug("message [%s] sent!!!", msg._id); homecoming msg._id; } else if (result == constants.event_emit_not_sent_and_not_stored) { applog.debug("message [%s] not sent", msg._id); throw new error("message not sent"); } }) .then(messageservice.remove) .then(function(result) { applog.debug("message deleted: [%s]", msg._id); }, function(err) { applog.error("the message has not been deleted: [%s]", msg._id); }); }

now can like

messageservice.findscheduled() .then(function(messages){ applog.debug("found [%d] stored messages",messages.length); homecoming q.all(messages.map(sendanddelete)); }) .then(function() { applog.debug("all messages done"); });

node.js callback promise q

Comments

Post a Comment

Popular posts from this blog

xslt - DocBook 5 to PDF transform failing with error: "fo:flow" is missing child elements. Required content model: marker* -

xslt - DocBook 5 to PDF transform failing with error: "fo:flow" is missing child elements. Required content model: marker* - i've inherited doc publishing process takes docbook , builds html , pdf output, using apache fop both. project had been started, never completed. lots of tweaking, i've able of doc sets build (20+), except handful, , fail severe code 1 of these 2 conditions: "fo:flow" missing kid elements. required content model: marker* "fo:block" not valid kid of "fo:root" the xml output comes out of docbook , docbook-fop checks out well-formed. the fop error in 1 book, "endecagloss", example, points end of string: <fo:flow flow-name="xsl-region-body" start-indent="4pc" end-indent="0pt"/> here’s log output in case: [java] severe: javax.xml.transform.transformerexception: file:/scratch/publishing/hudson/jobs/build-main-endeca-documentation/workspace/serverdoc/w...
Read more

mediawiki - How do I insert tables inside infoboxes on Wikia pages? -

mediawiki - How do I insert tables inside infoboxes on Wikia pages? - i want insert tables in infoboxes. example, have proteinbox i've developed using infobox template (http://health-and-medicine.wikia.com/wiki/template:proteinbox), , fasta field big fit comfortably in proteinbox. hence collapsible table within box. this tried: {{infobox | row 1 = {| class = "mw-collapsible mw-collapsed wikitable" |- | <!-- table content --> |} }} your problem is, putting nested table within template. pipe characters ( | ) in table syntax collides pipe usage in templates. the commonly used hack around create template called template:! , containing pipe character, , utilize when need set tables, parser functions or other stuff using pipe characters, within templates. table (with every | replaced {{!}} ): {{{!}} {{!}}- {{!}} a1 {{!}} b1 {{!}}- {{!}} a2 {{!}} b2 {{!}}} ...the equivalent of {| |- | a1 | b1 |- | a2 | b2 |} furthermore, hav...
Read more

Local Service User Logged into Windows -

Local Service User Logged into Windows - i created windows service tracks app server user connected through load balancer. it retrieves user logged windows on machine, cross references active directory (ad) business relationship homecoming first name, lastly name , e-mail (for notification through website created project) there 1 scheme on network users remote system, vista system, reason returning values "local service" logged machine, it's weird , security guys impossible "local service" business relationship logged windows. here how user logged windows managementscope ms = new managementscope("\\\\.\\root\\cimv2"); objectquery query = new objectquery("select * win32_computersystem"); managementobjectsearcher searcher = new managementobjectsearcher(ms, query); foreach (managementobject mo in searcher.get()) { _username = mo["username"].tostring(); } // remove domain part username string[] usernameparts = _...
Read more