作为承诺的结果表示重新发送 [英] express res.send as result of promise

问题描述

我不明白发生了什么事...

I'm not understanding what's going on...

使用q许诺，这行得通:

const deferred = q.defer();
deferred.resolve('Hellow');

const myPromise = deferred.promise;

router.get('/items', (req, res) => {
    myPromise.then((result) => res.send(result));
});

但这不是，它使浏览器像请求永无止境一样

but this doesn't, it keeps the browser like if the request never ends:

router.get('/items', (req, res) => {
    myPromise.then(res.send);
});

怎么了?

推荐答案

以下是与res.send相关的express库的片段:

Below is the fragment of the express library related to res.send:

res.send = function send(body) {
    var chunk = body;
    var encoding;
    var len;
    var req = this.req;
    var type;

    // settings
    var app = this.app;

    // allow status / body
    if (arguments.length === 2) {
        // res.send(body, status) backwards compat
        if (typeof arguments[0] !== 'number' && typeof arguments[1] === 'number') {
            deprecate('res.send(body, status): Use res.status(status).send(body) instead');
            this.statusCode = arguments[1];
        } else {
            deprecate('res.send(status, body): Use res.status(status).send(body) instead');
            this.statusCode = arguments[0];
            chunk = arguments[1];
        }
    }
 //.....

如您所见，有很多this引用.在您的情况下，myPromise.then(res.send) this指的是promise对象，而不是res，这就是您的代码不起作用的原因.

As you can see, there are lots of this references. In your case myPromise.then(res.send) the this refers to promise object, not to res, that's why your code doesn't work.

您可以使用 .bind 方法，因此this将引用res对象:

You can change the context by using .bind method, so this will refer to res object:

router.get('/items', (req, res) => {
    myPromise.then(res.send.bind(res));
});

这篇关于作为承诺的结果表示重新发送的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！