javascript - 将 promise 的包装快速路由返回到 app.use()

Question

我希望使快速路线更加模块化。我对使用 Promise 读取文件然后返回路由感兴趣。

代码如下:

var express = require('express')
var router = express.Router()
var app = express()

var Promise = require("bluebird")
var fs = Promise.promisifyAll(require("fs"))

function promiseRoute(file){
  return fs.readFileAsync(file, "utf8")
  .then(JSON.parse)
  .then(function(file){
    if(!file.url) throw new Error("missing url")
    router.get(file.url, function(req, res, next){
      return res.redirect("/hello")
    })
    return router
  })
}

app.use(promiseRoute("../file.json"))

var server = app.listen(3000, function () {})

也尝试过

promiseRoute(path.join(__dirname, "./file.json")).then(app.use)

我收到此错误。

throw new TypeError('app.use() requires middleware functions')

这是有 promise 的。

Unhandled rejection TypeError: Cannot read property 'lazyrouter' of undefined
    at use (/project/node_modules/express/lib/application.js:213:7)
    at tryCatcher (/project/node_modules/bluebird/js/main/util.js:24:31)
    at Promise._settlePromiseFromHandler (/project/node_modules/bluebird/js/main/promise.js:489:31)
    at Promise._settlePromiseAt (/project/node_modules/bluebird/js/main/promise.js:565:18)
    at Promise._settlePromises (/project/node_modules/bluebird/js/main/promise.js:681:14)
    at Async._drainQueue (/project/node_modules/bluebird/js/main/async.js:123:16)
    at Async._drainQueues (/project/node_modules/bluebird/js/main/async.js:133:10)
    at Immediate.Async.drainQueues [as _onImmediate] (/project/node_modules/bluebird/js/main/async.js:15:14)
    at processImmediate [as _immediateCallback] (timers.js:371:17)

也尝试过这个:

promiseRoute(path.join(__dirname, "./file.json")).then(function(router){
  app.use(function(req, res, next){
    return router
  })
})

如何将 promise /路由返回到app.use？

Answer 1

app.use需要中间件功能。也就是说，一个采用 (req, res, next) 的函数。

总体来说:

app.use(function(req, res, next){
     promiseRoute(probably_pass_things_in).nodeify(next);
});

nodeify 是将 promise 转换为 next 将采取的回调。请注意，您可以使用用于 Express 的第三方 Promise 中间件。