node.js 如何使用猫鼬 Promise - mongo
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How to use mongoose Promise - mongo
提问by user600314
Can someone give me an example on how to use a Promise with mongoose. Here is what I have, but its not working as expected:
有人能给我一个关于如何使用 Promise 和 mongoose 的例子吗？这是我所拥有的，但它没有按预期工作：
app.use(function (req, res, next) {
res.local('myStuff', myLib.process(req.path, something));
console.log(res.local('myStuff'));
next();
});
and then in myLib, I would have something like this:
然后在 myLib 中，我会有这样的事情：
exports.process = function ( r, callback ) {
var promise = new mongoose.Promise;
if(callback) promise.addBack(callback);
Content.find( {route : r }, function (err, docs) {
promise.resolve.bind(promise)(err, docs);
});
return promise;
};
At some point I am expecting my data to be present, but how can I access it, or get at it?
在某些时候，我希望我的数据存在，但我如何访问或获取它？
回答by Alexander Shtuchkin
In the current version of Mongoose, the exec()method returns a Promise, so you can do the following:
在当前版本的 Mongoose 中，该exec()方法返回一个 Promise，因此您可以执行以下操作：
exports.process = function(r) {
return Content.find({route: r}).exec();
}
Then, when you would like to get the data, you should make it async:
然后，当您想要获取数据时，您应该使其异步：
app.use(function(req, res, next) {
res.local('myStuff', myLib.process(req.path));
res.local('myStuff')
.then(function(doc) { // <- this is the Promise interface.
console.log(doc);
next();
}, function(err) {
// handle error here.
});
});
For more information about promises, there's a wonderful article that I recently read: http://spion.github.io/posts/why-i-am-switching-to-promises.html
有关 promise 的更多信息，我最近阅读了一篇精彩的文章：http: //spion.github.io/posts/why-i-am-switching-to-promises.html
回答by konsumer
Mongoose already uses promises, when you call exec()on a query.
当您调用exec()查询时，Mongoose 已经使用了 Promise。
var promise = Content.find( {route : r }).exec();
回答by Alexey B.
Mongoose 4.0 brings some exciting new functionality: schema validation in the browser, query middleware, validation on update, and promises for async operations.
Mongoose 4.0 带来了一些令人兴奋的新功能：浏览器中的模式验证、查询中间件、更新验证和异步操作承诺。
With [email protected]you can use any promises that you want
使用[email protected]，您可以使用任何您想要的承诺
var mongoose = require('mongoose');
mongoose.Promise = require('bluebird');
Another example with polyfilling global.Promise
另一个 polyfilling global.Promise 的例子
require('es6-promise').polyfill();
var mongoose = require('mongoose');
So, you can just do later
所以，你可以稍后再做
Content
.find({route : r})
.then(function(docs) {}, function(err) {});
Or
或者
Content
.find({route : r})
.then(function(docs) {})
.catch(function(err) {});
P.S. Mongoose 5.0
PS猫鼬5.0
Mongoose 5.0 will use native promises by defaultif available, otherwise no promises. You will still be able to set a custom promises library using
mongoose.Promise = require('bluebird');, however, mpromise will not be supported.
如果可用，Mongoose 5.0 将默认使用本机承诺，否则不使用承诺。您仍然可以使用 设置自定义承诺库
mongoose.Promise = require('bluebird');，但是，将不支持 mpromise。
回答by deedubs
I believe you're looking for
我相信你正在寻找
exports.process = function ( r, callback ) {
var promise = new mongoose.Promise;
if(callback) promise.addBack(callback);
Content.find( {route : r }, function (err, docs) {
if(err) {
promise.error(err);
return;
}
promise.complete(docs);
});
return promise;
};
回答by Mr.Thanks
On this page:http://mongoosejs.com/docs/promises.html
在此页面上：http: //mongoosejs.com/docs/promises.html
The title is Plugging in your own Promises Library
标题是插入你自己的 Promises 库
回答by Anthony
Use the bluebird Promise library like this:
像这样使用 bluebird Promise 库：
var Promise = require('bluebird');
var mongoose = require('mongoose');
var mongoose = Promise.promisifyAll(mongoose);
User.findAsync({}).then(function(users){
console.log(users)
})
This is thenable, such as:
这是可以的，例如：
User.findAsync({}).then(function(users){
console.log(users)
}).then(function(){
// more async stuff
})
