[英]Using native ES6 promises with MongoDB
I'm aware that the Node driver for Mongo can be promisified using external libraries. 我知道可以使用外部库来宣传 Mongo的Node驱动程序。 I was curious to see if ES6 promises could be used with
MongoClient.connect
, so I tried this (using Babel 5.8.23 to transpile): 我很想知道ES6的承诺是否可以与
MongoClient.connect
一起使用,所以我尝试了这个(使用Babel 5.8.23进行转换):
import MongoClient from 'mongodb';
function DbConnection({
host = 'localhost',
port = 27017,
database = 'foo'
}) {
return new Promise((resolve, reject) => {
MongoClient.connect(`mongodb://${host}:${port}/${database}`,
(err, db) => {
err ? reject(err) : resolve(db);
});
});
}
DbConnection({}).then(
db => {
let cursor = db.collection('bar').find();
console.log(cursor.count());
},
err => {
console.log(err);
}
);
The output is {Promise <pending>}
. 输出为
{Promise <pending>}
。 Anything to do with cursors seems to yield a similar result. 与游标有关的任何事情似乎都会产生类似的结果。 Is there a way to get around this or am I barking up the wrong tree entirely?
有没有办法解决这个问题,还是我完全咆哮错误的树?
Edit: node version 4.1.0. 编辑:节点版本4.1.0。
There is nothing to get around, this is the expected behavior. 没有什么可以解决的,这是预期的行为。
cursor.count()
returns a promise, if you want the value, you need to use .then
, eg cursor.count()
返回一个promise,如果你想要这个值,你需要使用.then
,例如
DbConnection({}).then(
db => {
let cursor = db.collection('bar').find();
return cursor.count();
}
}).then(
count => {
console.log(count);
},
err => {
console.log(err);
}
);
or simplified 或简化
DbConnection({}).then(db => db.collection('bar').find().count()).then(
count => console.log(count),
err => console.log(err)
);
Another syntax for the response of loganfsmyth (thanks by the way) loganfsmyth响应的另一种语法(顺便说一下)
cursor.count().then(function(cursor_count){
if(cursor_count){
// use cursor
}else{
// no results
}
}
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