如何简单地以字符串的形式同步获取一个url体 [英] how to simply fetch an url body as a string synchronously

问题描述

您如何简单实现此函数：

How would you simply implement this function:

String fetchUrlBodyAsString(String url) {
  ...
}

用法：

String schema = fetchUrlBodyAsString("http://json-schema.org/draft-04/schema#");

此主题使用dart下载文件解释了从主函数获取数据的好方法。但如果你尝试它，你看到真正的工作发生后离开主。我认为我想创建的同步函数很难使用HttpClient，因为它试图让异步api同步工作。根据此线程可能无法实现： https：/ /groups.google.com/a/dartlang.org/d/msg/misc/kAgayQyaPhQ/wonJ776_FGIJ

This thread Using dart to download a file explains a good way to get to the data from a main function. But if you try it you see that the real work happens after leaving main. I think that the synchronous function that I want to create is difficult using HttpClient because it is trying to get an async api to work synchronously. According to this thread that may not be possible: https://groups.google.com/a/dartlang.org/d/msg/misc/kAgayQyaPhQ/wonJ776_FGIJ

什么是Dart的实现方式非浏览器/控制台设置？

What is a Dart way to implement this in a non-browser/console setting?

推荐答案

使用异步方法真的很有感染力。一旦你开始在函数中使用 Future ，你必须返回一个 Future 作为结果。因此，您的 fetchUrlBodyAsString 函数可以如下所示：

The using of asynchronous methods is really infectious. Once you start using Future inside a function you have to return a Future as result. So your fetchUrlBodyAsString function can look like :

import 'dart:io';
import 'dart:async';

Future<String> fetchUrlBodyAsString(String url) =>
  new HttpClient().getUrl(Uri.parse(url))
    .then((HttpClientRequest request) => request.close())
    .then((HttpClientResponse response) =>
        response.transform(new StringDecoder()).join());

main() {
  final url = "http://json-schema.org/draft-04/schema#";
  Future<String> schema = fetchUrlBodyAsString(url);
  schema.then(handleContent);
}

handleContent(String content) {
  print(content); // or do what you want with content.
}

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