coffeescript - Coffescript Nested Do Loop / Async Nested Loop -

i want save 2 collections in mongodb. operations async use , in coffee.

for machine in machines   do(machine) ->     //if machine not exist       part in machine.parts         do(part) ->           //if not part not exists --> save           //push part machine parts list       //save machine 

the machine parts empty later in db. how can make first loop wait second loop finish?

edit real code example:

  recipemodel = require('../models/recipe.model')   ingredientmodel = require('../models/ingredient.model')    #save recipe database   async.map recipes, (recipe, next) ->     recipedbobject = new recipemodel()     recipedbobject.href = recipe.href     recipedbobject.ingredients = []     recipemodel.find({ href: recipe.href }, (err, recipefound) ->       return next err if err       return next null, recipefound if recipefound.length > 0        recipedbobject.title = recipe.title       ingredientspusharray = []       console.log recipe.href        async.map recipe.zutaten, (ingredient, cb) ->         #save ingredients         ingredient.idname = ingredient.name.replace(/[^a-za-z0-9]+/gi, "").tolowercase()         ingredientmodel.find({ idname: ingredient.idname }, (err, ingredientfound) ->           return next err if err           if ingredientfound.length >0             ingredientdbobject = ingredientfound[0]           else             ingredientdbobject = new ingredientmodel()            ingredientdbobject.name = ingredient.name           ingredientdbobject.save()            recipedbobject.ingredients.push({"idname":ingredient.idname, "name":ingredient.name, "amount":ingredient.amount})           return cb(null, true)         )       recipedbobject.ingredients = ingredientspusharray       recipedbobject.save()       return next(null, true)     ) 

i still don't working. recipes saved, node builds ingredients array neither saves ingredients nor save array recipes.

edit 2:

  async.map recipes,     (recipe, next) ->       recipedbobject = new recipemodel()       recipedbobject.href = recipe.href       recipedbobject.ingredients = []       recipemodel.find({ href: recipe.href }, (err, recipefound) ->         return next err if err         return next null, recipefound if recipefound.length > 0          recipedbobject.title = recipe.title         ingredientspusharray = []          ingredientsarray = []         async.map recipe.zutaten,           (ingredient, cb) ->             #save ingredients             ingredient.idname = ingredient.name.replace(/[^a-za-z0-9]+/gi, "").tolowercase()             ingredientmodel.find({ idname: ingredient.idname }, (err, ingredientfound) ->               return next err if err               ingredientsarray.push({"idname":ingredient.idname, "name":ingredient.name, "amount":ingredient.amount})               if ingredientfound.length >0                 return cb(null, true)               else                 ingredientdbobject = new ingredientmodel()                 ingredientdbobject.name = ingredient.name                 ingredientdbobject.idname = ingredient.idname                 ingredientdbobject.save((err) ->                   #console.log "some erros because required empty" if err                   return cb err if err                   #console.log "ingredient saved"                   return cb(null, true)                 )           (err, ingredientsarray) ->             console.log "this never logged"             return err if err             recipedbobject.ingredients = ingredientsarray             recipedbobject.save((err)->               return err if err               return next(null, true)           )         )       )     (err) ->       console.log "show me errors: ", err if err 

now ingredients saved recipes aren't.

interesting ressources: http://www.hacksparrow.com/managing-nested-asynchronous-callbacks-in-node-js.html

the easiest way use module for managing asynchronous control flow, example

• async
• promise-based solutions (e.g. when, bluebird, q)
• co es6 generator-based control flow

here simple examples.

using async.map

async = require 'async'  async.map machines,   (machine, next) ->     # process single machine object     machine.findbyid machine._id, (err, found) ->       return next err if err # return error       return next null, found if found # return object found       async.map machine.parts,         (part, cb) ->           # save part db , call cb callback afterward           part.create part, cb         (err, parts) ->           return next err if err # propagate error next handler           # parts have been saved           machine.parts = parts           # save machine db , call next callback afterward           machine.create machine, next   (err, machines) ->     if err       # went wrong     else       # machine objects have been processed 

using promises , when module

when = require 'when'  machines_to_save = when.filter machines, ({_id}) ->   machine.findbyid(_id).then (found) -> not found when.map machines_to_save, (machine) ->   when.map machine.parts, (part) ->     part.create part   .then (parts) ->     machine.parts = parts     machine.create machine .then (saved_machines) ->   # machines saved .otherwice (err) ->   # went wrong