将bluebird用于猫鼬，得到".bind不是函数". [英] Use bluebird for mongoose, got ".bind is not a function"

问题描述

我将 bluebird 用于

我想使用 Promise.bind 在承诺链:

function getAutherOfBook(name)
{
    return Book.findOne(
        {
            name: name
        }, "-_id auther")
        .then(doc =>
        {
            return doc.auther;
        });
};


function geNationalityOfAuther(name)
{
    return Auther.findOne(
        {
            name: name
        }, "-_id nationality")
        .then(doc =>
        {
            return doc.nationality;
        });
};


getAutherOfBook("The Kite Runner")
    .bind({})
    .then(auther =>
    {
        this.auther = auther;
        return geNationalityOfAuther(auther);
    })
    .then(nationality =>
    {
        console.log("auther: ", this.auther);
        console.log("nationality: ", nationality);
    })
    .bind()

但是我得到了一个错误: getAutherOfBook(...).bind不是一个函数

But I got the error: getAutherOfBook(...).bind is not a function

也许蓝鸟不适用于猫鼬?

Maybe bluebird is not working for mongoose?

推荐答案

您遇到的问题是猫鼬查询不会返回完整的承诺-直接引用

The problem you are having is that mongoose queries does not return full fledge promises -- directly quoting http://mongoosejs.com/docs/promises.html (v4.7.6)

// A query is not a fully-fledged promise, but it does have a `.then()`.
query.then(function (doc) {
  // use doc
});

// `.exec()` gives you a fully-fledged promise
var promise = query.exec();
assert.ok(promise instanceof require('mpromise'));

换句话说，then函数是语法糖而不是promise，这就是为什么bind和其他promise函数不起作用的原因.

In other words, the then function is syntax sugar and not a promise which is why the bind and other promise functions does not work.

要使其正常工作，您可以将其包装成完整的承诺，也可以按照文档中的建议使用exec函数

To make it work, you either wrap it up in a full promise or use the exec function as suggested in the docs

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