Using wait.for with nodejs and mongoskin to avoid callback hell

问题

I m actually developping a little application with mongodb and nodejs to create my REST Api. I face a problem when I need to access an object reference :

I have a roadmap collection which reference a user object
When I want to get all the roadmaps, I have to loop on my roadmap array to lazy load my users, by the ref ID stored in the roadmap collection
I have a callback problem, the user is not loaded when I need it

I have found a solution using Wait.for library : https://github.com/luciotato/waitfor , but I dont know how it works. I tried everything, but no way to make it work

all: (req,res)->
    @em.collection(@collection).find().toArray((err, result)=>
      roadmaps = []
      for r in result
        r.user = @getUser(r.user.oid)
        roadmaps.push r
      res.send(roadmaps))



 getUser: (oid)->
    @em.collection('user').findOne {_id: new @objectId(oid)}, (err, res)=>
      if !err
        return res
      return undefined

Does anybody have an idea of how to make it works properly ? Where should I put the wait.lauchFiber ? where should I put the wait.for ?

Thanks for all

回答1:

I'm not familiar with CoffeeScript, please correct me and I'll edit this answer.

all: (req,res)->
    var result = wait.forMethod(@em.collection(@collection).find(), "toArray")
    roadmaps = []
    for r in result
        r.user = @getUser(r.user.oid)
        roadmaps.push r
    res.send(roadmaps)



 getUser: (oid)->
    try
      return wait.forMethod(@em.collection('user'),"findOne",{_id:new @objectId(oid)})
    catch(err)
      return undefined

As you can see, for "getUser", if the method is that simple, you better use your version, with the callback.

"where to put the launchFiber()?"

you put the launchFiber when a request arrives. see https://github.com/luciotato/waitfor#proper-use

来源：https://stackoverflow.com/questions/25442470/using-wait-for-with-nodejs-and-mongoskin-to-avoid-callback-hell

标签

node.js

mongodb

coffeescript

mongoskin