如何从我试图在字符串中抓取的网页中获取 html？

如何解决如何从我试图在字符串中抓取的网页中获取 html？

我编写了以下代码：

require "http/client"
require "myhtml"

puts "Give me the URL of the page to be scraped."

url = gets

html=<<-HTML
 [Here goes the html of the website to be scraped]
HTML

myhtml = Myhtml::Parser.new(html)

myhtml.nodes(:div).each do |node|
  id = node.attribute_by("id")

  if first_link = node.scope.nodes(:a).first?
    href = first_link.attribute_by("href")
    link_text = first_link.inner_text

    puts "div with id #{id} have link [#{link_text}](#{href})"
  else
    puts "div with id #{id} have no links"
  end
end

如何从我试图抓取的网页中获取 html 以替换字符串

html=<<-HTML
 [Here goes the html of the website to be scraped]
HTML

类似的东西

response = requests.get(url)

html = BeautifulSoup(response.text,'html.parser')

来自以下 Python 代码：


url = input("What is the address of the web page in question?\n")

response = requests.get(url)

html = BeautifulSoup(response.text,'html.parser')

或 let html = reqwest::get(url).await?.text().await?; 来自以下 Rust 代码：

println!("Give me the URL of the page to be scraped."); 
 let mut url = String::new();
 io::stdin().read_line(&mut url).expect("Failed to read line");

 let html = reqwest::get(url).await?.text().await?;

shard myhtml 的文档没有提供足够的例子让我弄清楚这一点。可以用 Crystal's HTTP client 从他们的标准库？当我更换

html=<<-HTML
 [Here goes the html of the website to be scraped]
HTML

与

response = HTTP::Client.get url

html = response.body

我收到以下错误：

response = HTTP::Client.get url #no overload matches 'HTTP::Client.get' with type (String | Nil)
                             ^--
Error: no overload matches 'HTTP::Client.get' with type (String | Nil)

Overloads are:
 - HTTP::Client.get(url : String | URI,headers : HTTP::Headers | ::Nil = nil,body : BodyType = nil,tls : TLSContext = nil)
 - HTTP::Client.get(url : String | URI,tls : TLSContext = nil,&block)
 - HTTP::Client.get(url,*,form : String | IO | Hash)
 - HTTP::Client.get(url,form : String | IO | Hash,&block)
Couldn't find overloads for these types:
 - HTTP::Client.get(Nil)

我能够从网页中获取文本通过硬编码，例如response = HTTP::Client.get "https://github.com/monero-project/monero/releases" 但这还不够，因为我希望应用程序具有交互性。

解决方法

你已经接近了，抱怨的是类型系统。 HTTP::Client.get 需要 String（或者更确切地说是 String | URL）。但是，在您的代码中，您的 url 变量也可以是 nil 并且属于 String? 类型，它是 String | Nil 的缩写。如果您对 URL 进行硬编码，则它不能是 nil，而始终是 String 类型。因此 HTTP::Client.get 调用有效。

查看documentation of the get function：

def gets(chomp = true) : 字符串？

从此 IO 中读取一行。一行以 \n 字符结束。如果在此 IO 结束时调用，则返回 nil。

有多种方法可以解决它，但基本思想是您必须确保在进行 HTTP 调用时 url 不能为 nil。例如：

url = gets
if url
  # now url cannot be nil
  response = HTTP::Client.get url
  html = response.body
  puts html
end

进一步阅读：if var