NodeJs在飞镖中请求回调

Question

我试图将下面的Node.js代码片段转换为Dart。在我的转换中，只要有响应，就会立即打印'data returned ...'消息，与Node.js版本不同，该版本等待页面完成所请求的2秒延迟。

Node.js的

var http = require('http')  
function fetchPage() { 
    console.log('fetching page'); 
    http.get({ host: 'trafficjamapp.herokuapp.com', path: '/?delay=2000' }, function(res) { 
    console.log('data returned from requesting page'); 
    }).on('error', function(e) { 
    console.log("There was an error" + e); 
    }); 
} 

飞镖

import 'dart:io'; 
import 'dart:uri'; 

fetchPage() { 
    print('fetching page'); 
    var client = new HttpClient(); 
    var uri = new Uri.fromComponents(scheme:'http', domain: 'trafficjamapp.herokuapp.com', path: '?delay=2000'); 
    var connection = client.getUrl(uri); 

    connection.onRequest = (HttpClientRequest req) { 
    req.outputStream.close(); 
    }; 

    connection.onResponse = (HttpClientResponse res){ 
    print('data returned from requesting page'); 
    }; 

    connection.onError = (e) => print('There was an error' ' $e'); 
} 

如何实现达特相同延迟打印中的节点？提前致谢。

Answer 1

您的DART代码几乎是正确的，但有一个错误。您应该使用query命名参数而不是path。我真的不知道哪个Url与您的代码通话，但是响应的状态码为400。为了获得更多可读性，您还可以使用Uri.fromString构造函数。

此外，您可以省略您的onRequest设置，因为在未定义onRequest时完成相同的代码。

下面的代码：

import 'dart:io'; 
import 'dart:uri'; 

main() { 
    print('fetching page'); 
    //var uri = new Uri.fromString('http://trafficjamapp.herokuapp.com/?delay=2000'); 
    var uri = new Uri.fromComponents(scheme:'http', 
     domain: 'trafficjamapp.herokuapp.com', query: 'delay=2000'); 
    var client = new HttpClient(); 
    var connection = client.getUrl(uri); 
    connection.onResponse = (HttpClientResponse res){ 
    print('data returned from requesting page with status ${res.statusCode}'); 
    }; 
    connection.onError = (e) => print('There was an error' ' $e'); 
} 

Answer 2

您可以将onResponse回调的文档中找到这样的：当接收到响应的所有页眉和数据准备接收

回调被调用。

所以它的工作原理是这样的：

connection.onResponse = (res) { 
    print('Headers received, can read the body now'); 
    var in = res.inputStream; 

    in.onData =() { 
    // this can be called multiple times 
    print('Received data'); 
    var data = in.read(); 
    // do something with data, probably? 
    }; 
    in.onClosed =() { 
    // this is probably the event you are interested in 
    print('No more data available'); 
    }; 
    in.onError = (e) { 
    print('Error reading data: $e'); 
    }; 
};