执行几个猫鼬疑问：如何使用的承诺呢？ [英] Executing several mongoose queries: how to use promises instead?

问题描述

我有以下的code和我想避免嵌套的回调：

I have the following code and I would like to avoid nested callbacks:

app.get '/performers', (req, res) ->
    conductor = require('models/conductor').init().model
    soloist = require('models/soloist').init().model
    orchestra = require('models/orchestra').init().model
    chamber = require('models/chamber').init().model
    performers = {}
    conductor.find {}, (err, result) ->
        performers.conductor = result
        soloist.find {}, (err, result) ->
            performers.soloist = result
            orchestra.find {}, (err, result) ->
                performers.orchestra = result
                chamber.find {}, (err, result) ->
                    performers.chamber = result
                    res.json performers

任何想法？

推荐答案

我觉得 异步 库比对承诺这样的事情一个清晰的解决方案。对于这个特定的情况下， async.parallel 将工作做好。

I find the async library to be a cleaner solution than promises for this sort of thing. For this specific case, async.parallel would work well.

我不是太熟悉的CoffeeScript，但它会是这个样子：

I'm not overly familiar with coffeescript, but it would look something like this:

performers = {}
async.parallel [
    (callback) ->
        conductor.find {}, (err, result) ->
            performers.conductor = result
            callback err
    (callback) ->
        soloist.find {}, (err, result) ->
            performers.soloist = result
            callback err
    (callback) ->
        orchestra.find {}, (err, result) ->
            performers.orchestra = result
            callback err
    (callback) ->
        chamber.find {}, (err, result) ->
            performers.chamber = result
            callback err
    ], (err) ->
        res.json performers

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