Node.js承诺与mongoskin [英] Node.js promises with mongoskin

问题描述

我正在尝试避免在制作mongodb查询时使用回调。我正在使用mongoskin来打电话，如下所示：

I'm trying to avoid using callbacks when making mongodb queries. I'm using mongoskin to make calls like so:

req.db.collection('users').find().toArray(function (err, doc) {
  res.json(doc);
});

在许多情况下，我需要进行多个查询，所以我想使用Node.js promise库，但是不知道如何把这些功能作为承诺。我看到的大多数例子对于 readFile 这样的事情来说是微不足道的，我猜这个例子我需要以某种方式包装到Array？这可以完成还是必须由mongoskin实现？

In many cases I need to make multiple queries so I want to use Node.js promise library but I'm not sure how to wrap these functions as promises. Most of the examples I see are trivial for things like readFile, I'm guessing in this case I would need to wrap toArray somehow? Can this be done or would have to be something implemented by mongoskin?

一个例子可以是任何一组回调，find / insert，find / find / insert，find /更新：

An example could be any set of callbacks, find/insert, find/find/insert, find/update:

req.db.collection('users').find().toArray(function (err, doc) {
  if (doc) {
    req.db.collection('users').find().toArray(function (err, doc) {
      // etc...
    });
  }
  else {
    // err
  }
});

推荐答案

您可以用蓝鸟来表达整个模块：

You can promisify the entire module like so with bluebird:

var Promise = require("bluebird");
var mongoskin = require("mongoskin");
Object.keys(mongoskin).forEach(function(key) {
  var value = mongoskin[key];
  if (typeof value === "function") {
    Promise.promisifyAll(value);
    Promise.promisifyAll(value.prototype);
  }
});
Promise.promisifyAll(mongoskin);

这只需要在您的应用程序中一次完成，而不需要在应用程序中的任何位置

This only needs to be done in one place for one time in your application, not anywhere in your application code.

之后，您只需使用正常方式，除了Async后缀，并且不传递回调：

After that you just use methods normally except with the Async suffix and don't pass callbacks:

req.db.collection('users').find().toArrayAsync()
  .then(function(doc) {
    if (doc) {
      return req.db.collection('users').find().toArrayAsync();
    }
  })
  .then(function(doc) {
    if (doc) {
      return req.db.collection('users').find().toArrayAsync();
    }
  })
  .then(function(doc) {
    if (doc) {
      return req.db.collection('users').find().toArrayAsync();
    }
  });

---

所以再次，如果你调用一个函数， / p>

---

So again, if you call a function like

foo(a, b, c, function(err, result) {
    if (err) return console.log(err);
    //Code
});

承诺返回版本称为：

fooAsync(a, b, c).then(...)

（未收到的错误会自动记录，所以如果您只需要登录，则不需要检查它们）

(Uncaught errors are automatically logged so you don't need to check for them if you are only going to log it)

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