节点JS：res.render（）之后res.download（）错误 [英] Node JS : Error with res.download() after res.render()

问题描述

我从Node JS开始，但出现错误：

I'm beginning with Node JS, and I get an error :

错误：发送标头后无法设置标头。

Error: Can't set headers after they are sent.

您可以看到我的代码，问题出在 res.download（）;
或者，如何显示没有 res.render（）的视图？

You can see my code, the problem is with res.download(); Or, how can I show the view without res.render()?

你能告诉我吗我该如何解决此问题？谢谢！

Can you tell me how to fix this issue? Thanks you!

var express = require('express');
var app = express();
var pythonShell = require('python-shell');

app.set('view engine', 'ejs');
app.use(express.static('style'));

app.post('/downloads', function(req, res) {                                 
  res.render('downloads.ejs');
  console.log("Python script begins");
  pythonShell.run('./generator.py', function (err) {
    if (err) throw err;
    console.log("Python Script Ended");
    res.download('mapCreated.tiff', 'map.tiff');
  });
})

推荐答案

您要在之后发送 res.download res.render 。这将尝试再次发送响应，但是您不能两次发送响应。这就是导致错误的原因错误：发送标头后无法设置标头。

You are sending res.download after res.render. this will try to send the response again, but you can't send response two times. That is what is causing the error Error: Can't set headers after they are sent.

您需要的首先要做的是渲染视图（您可以发送 get 请求来渲染视图），加载后，调用另一条路径来下载文件（发送 post 下载路径）

What you need to do is render the view first( you can send a get request to render the view) and when that view is loaded, call another route to download the file( send post route to download)

app.get('/downloads', function(req, res) { 
    res.render('downloads.ejs');
});

app.post('/downloads', function (req,res){
    console.log("Python script begins");
    pythonShell.run('./generator.py', function (err) { 
        if (err) throw err; 
        console.log("Python Script Ended");
        res.download('mapCreated.tiff', 'map.tiff');
    }); 
})

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