ruby - 如何使用正则表达式转换 Markdown 样式的链接？

Question

我正在尝试编写一个正则表达式来替换 markdown 样式的链接，但它似乎不起作用。这是我目前所拥有的:

# ruby code:
text = "[link me up](http://www.example.com)"
text.gsub!(%r{\[(\+)\]\((\+)\)}x, %{<a target="_blank" href="\\1">\\2</a>})

我做错了什么？

Answer 1

irb(main):001:0> text = "[link me up](http://www.example.com)"
irb(main):002:0> text.gsub /\[([^\]]+)\]\(([^)]+)\)/, '<a href="\2">\1</a>'
#=> "<a href=\"http://www.example.com\">link me up</a>"

我们可以为 Ruby 的正则表达式使用 extended 选项，让它看起来不像一只猫跳到键盘上:

def linkup( str )
  str.gsub %r{
    \[         # Literal opening bracket
      (        # Capture what we find in here
        [^\]]+ # One or more characters other than close bracket
      )        # Stop capturing
    \]         # Literal closing bracket
    \(         # Literal opening parenthesis
      (        # Capture what we find in here
        [^)]+  # One or more characters other than close parenthesis
      )        # Stop capturing
    \)         # Literal closing parenthesis
  }x, '<a href="\2">\1</a>'
end

text = "[link me up](http://www.example.com)"
puts linkup(text)
#=> <a href="http://www.example.com">link me up</a>

请注意，对于其中包含右括号的 URL，上述操作将失败，例如

linkup "[O](http://msdn.microsoft.com/en-us/library/ms533050(v=vs.85).aspx)"
# <a href="http://msdn.microsoft.com/en-us/library/ms533050(v=vs.85">O</a>.aspx)

如果这对您很重要，您可以将 [^)]+ 替换为 \S+(?=\)) 这意味着 “找到尽可能多的尽可能使用非空白字符，但要确保之后有 )"。

---

要回答您的问题“我做错了什么”，您的正则表达式是这样说的:

%r{
  \[      # Literal opening bracket   (good)
    (     # Start capturing           (good)
      \+  # A literal plus character  (OOPS)
    )     # Stop capturing            (good)
  \]      # Literal closing bracket   (good)
  \(      # Literal opening paren     (good)
    (     # Start capturing           (good)
      \+  # A literal plus character  (OOPS)
    )     # Stop capturing            (good)
  \)      # Literal closing paren     (good)
}x