ヘッダーを送信後に設定することはできません。 Nodejs/express with axios

Question

私はこのエラーを見て、それを回避する方法をもっと知りたいだけです。私はjsonオブジェクトとしてデータを出力できる必要があります。これを回避する方法はありますか？

私は基本的にチュートリアルからコピーして貼り付けていますが、なぜ深いリクエストを除いてここに取得しているのかわかりません。ここで

は誤りである：ここでは

Error: Can't set headers after they are sent. 
[0]  at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11) 
[0]  at ServerResponse.header (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\express\lib\response.js:730:10) 
[0]  at ServerResponse.send (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\express\lib\response.js:170:12) 
[0]  at ServerResponse.json (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\express\lib\response.js:256:15) 
[0]  at C:/Users/Amazo/Thrifa/moovr/src/server/API/routes/offers.js:28:21 
[0]  at Promise.<anonymous> (C:/Users/Amazo/Thrifa/moovr/src/server/API/controllers/store/OfferController.js:25:7) 
[0]  at Promise.<anonymous> (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mpromise\lib\promise.js:177:8) 
[0]  at emitOne (events.js:77:13) 
[0]  at Promise.emit (events.js:169:7) 
[0]  at Promise.emit (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mpromise\lib\promise.js:84:38) 
[0]  at Promise.fulfill (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mpromise\lib\promise.js:97:20) 
[0]  at C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\query.js:1406:13 
[0]  at model.Document.init (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\document.js:254:11) 
[0]  at completeOne (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\query.js:1404:10) 
[0]  at Immediate.cb (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\query.js:1158:11) 
[0]  at Immediate._onImmediate (C:\Users\Amazo\Thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mquery\lib\utils.js:137:16) 
[0]  at processImmediate [as _immediateCallback] (timers.js:383:17) 

は、コードは次のとおりです。

import OfferController from '../controllers/store/OfferController'; 
import RequestManager from '../utils/RequestManager'; 
import axios from 'axios'; 

const offerRoutes = (app) => { 
    app.get('/API/offers', (req, res, next) => { 
    axios 
     .get(
     'https://d2fzm6xoa70bg8.cloudfront.net/login?auth=e4031de36f45af2172fa8d0f054efcdd8d4dfd62', 
    ) 
     .then((response) => { 
     axios 
      .get('https://d2fzm6xoa70bg8.cloudfront.net/offerfilter?', { 
      headers: { Token: response.data.token }, 
      }) 
      .then((response) => { 
      const { data } = response; 

      data.map((item, i) => { 
       OfferController.findOne({ offer: item.offer }, (err, result) => { 
       if (err) { 
        res.json({ 
        message: err, 
        }); 

        return; 
       } 
       res.json({ 
        message: 'Offer already exist', 
        result, 
       }); 
       }); 

       const params = { 
       offer: item.offer, 
       cert: item.cert, 
       txid: item.txid, 
       expires_in: item.expires_in, 
       expires_on: item.expires_on, 
       expired: item.expired, 
       height: item.height, 
       time: item.time, 
       category: item.category, 
       title: item.title, 
       quantity: item.quantity, 
       currency: item.currency, 
       sysprice: item.sysprice, 
       price: item.price, 
       ismine: item.ismine, 
       commission: item.commission, 
       offerlink: item.offerlink, 
       offerlink_guid: item.offerlink_guid, 
       offerlink_seller: item.offerlink_seller, 
       private: item.private, 
       safesearch: item.safesearch, 
       safetylevel: item.safetylevel, 
       paymentoptions: item.paymentoptions, 
       paymentoptions_display: item.paymentoptions_display, 
       alias_peg: item.alias_peg, 
       description: item.description, 
       alias: item.description, 
       address: item.address, 
       alias_rating: item.alias_rating, 
       alias_rating_count: item.alias_rating_count, 
       alias_rating_display: item.alias_rating_display, 
       geolocation: item.geolocation, 
       offers_sold: item.offers_sold, 
       }; 
       OfferController.create(params, (err, results) => { 
       if (err) { 
        console.log(err); 

        return; 
       } 

       res.write(results); 
       }); 
      }); 
      }) 
      .catch((err) => { 
      console.log('err 2nd request', err); 
      res.json({ 
       confirmation: 'fail after 2nd request', 
       message: err, 
      }); 
      }); 
     }) 
     .catch((err) => { 
     console.log('err 1st request'); 
     res.json({ 
      confirmation: 'fail before 2nd request', 
      message: err, 
     }); 
     }); 
    }); 
}; 
export default offerRoutes; 

Answer 1

あなたが設定で結果res.jsonへの複数の呼び出しを行うことを意味しますmapへの呼び出し内でごres.json(...)を持っています同じresインスタンスについては、Content-Typeヘッダーを複数回使用します。