执行几个 mongoose 查询:如何改用 Promise? [英] Executing several mongoose queries: how to use promises instead?

问题描述

我有以下代码，我想避免嵌套回调:

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

有什么想法吗?

推荐答案

我找到了 async图书馆是比这类事情的承诺更清洁的解决方案.对于这种特定情况，async.parallel 会很好用.

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.

我对 coffeescript 不太熟悉，但它看起来像这样:

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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