如何使用正则表达式从html字符串获取图像url

Thiha Aung 发表于 Dev

昂蒂哈（Thiha Aung）

我正在尝试使用正则表达式从html字符串中获取文本，这是我目前正在处理的：

extension String {
func regex (pattern: String) -> [String] {
    do {
        let regex = try NSRegularExpression(pattern: pattern, options: NSRegularExpressionOptions(rawValue: 0))
        let nsstr = self as NSString
        let all = NSRange(location: 0, length: nsstr.length)
        var matches : [String] = [String]()
        regex.enumerateMatchesInString(self, options: NSMatchingOptions(rawValue: 0), range: all) {
            (result : NSTextCheckingResult?, _, _) in
            if let r = result {
                let result = nsstr.substringWithRange(r.range) as String
                matches.append(result)
            }
        }
        return matches
    } catch {
        return [String]()
    }
}

模式是： <img[^>]+src\\s*=\\s*['\']([^'\"]+)['\"][^>]*>

我仍然无法从中获取图片网址，这意味着它返回了一个空数组。实际上我的html字符串中包含一张图片。UIWebView由于UITableView尺寸调整问题，我不想使用它。因此，我需要从中获取图片网址html并使用AlamofireImage在UIImageView中显示它。

任何帮助吗？这只是我需要获取的一个网址。

这是我的标签：

<img src="https://en.wikipedia.org/wiki/File:BH_LMC.png"/>

到：

https://en.wikipedia.org/wiki/File:BH_LMC.png

Ro Me My

描述

<img\b(?=\s)(?=(?:[^>=]|='[^']*'|="[^"]*"|=[^'"][^\s>]*)*?\ssrc=['"]([^"]*)['"]?)(?:[^>=]|='[^']*'|="[^"]*"|=[^'"\s]*)*"\s?\/?>

正则表达式可视化

此正则表达式将执行以下操作：

此正则表达式捕获整个IMG标签
将源属性值放入捕获组1，如果引号不存在，则不加引号。
允许属性使用单引号，双引号或不带引号
可以修改以验证任意数量的其他属性
避免可能导致难以解析HTML的困难情况

例子

现场演示

https://regex101.com/r/qW9nG8/1

示范文本

请注意第一行中我们要查找特定机器人的困难边缘情况。

<img onmouseover=' if ( 6 > 3 { funSwap(" src="NotTheDroidYourLookingFor.jpg", 6 > 3 ) } ; ' src="http://website/ThisIsTheDroidYourLookingFor.jpeg" onload="img_onload(this);" onerror="img_onerror(this);" data-pid="jihgfedcba" data-imagesize="ppew" />
some text

<img src="http://website/someurl.jpeg" onload="img_onload(this);" />
more text
<img src="https://en.wikipedia.org/wiki/File:BH_LMC.png"/>

比赛样本

捕获组0获取整个IMG标签
捕获组1仅获取src属性值

[0][0] = <img onmouseover=' funSwap(" src='NotTheDroidYourLookingFor.jpg", data-pid) ; ' src="http://website/ThisIsTheDroidYourLookingFor.jpeg" onload="img_onload(this);" onerror="img_onerror(this);" data-pid="jihgfedcba" data-imagesize="ppew" />
[0][1] = http://website/ThisIsTheDroidYourLookingFor.jpeg

[1][0] = <img src="http://website/someurl.jpeg" onload="img_onload(this);" />
[1][1] = http://website/someurl.jpeg

[2][0] = <img src="https://en.wikipedia.org/wiki/File:BH_LMC.png"/>
[2][1] = https://en.wikipedia.org/wiki/File:BH_LMC.png

解释

NODE                     EXPLANATION
----------------------------------------------------------------------
  <img                     '<img'
----------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char
----------------------------------------------------------------------
  (?=                      look ahead to see if there is:
----------------------------------------------------------------------
    \s                       whitespace (\n, \r, \t, \f, and " ")
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------
  (?=                      look ahead to see if there is:
----------------------------------------------------------------------
    (?:                      group, but do not capture (0 or more
                             times (matching the least amount
                             possible)):
----------------------------------------------------------------------
      [^>=]                    any character except: '>', '='
----------------------------------------------------------------------
     |                        OR
----------------------------------------------------------------------
      ='                       '=\''
----------------------------------------------------------------------
      [^']*                    any character except: ''' (0 or more
                               times (matching the most amount
                               possible))
----------------------------------------------------------------------
      '                        '\''
----------------------------------------------------------------------
     |                        OR
----------------------------------------------------------------------
      ="                       '="'
----------------------------------------------------------------------
      [^"]*                    any character except: '"' (0 or more
                               times (matching the most amount
                               possible))
----------------------------------------------------------------------
      "                        '"'
----------------------------------------------------------------------
     |                        OR
----------------------------------------------------------------------
      =                        '='
----------------------------------------------------------------------
      [^'"]                    any character except: ''', '"'
----------------------------------------------------------------------
      [^\s>]*                  any character except: whitespace (\n,
                               \r, \t, \f, and " "), '>' (0 or more
                               times (matching the most amount
                               possible))
----------------------------------------------------------------------
    )*?                      end of grouping
----------------------------------------------------------------------
    \s                       whitespace (\n, \r, \t, \f, and " ")
----------------------------------------------------------------------
    src=                     'src='
----------------------------------------------------------------------
    ['"]                     any character of: ''', '"'
----------------------------------------------------------------------
    (                        group and capture to \1:
----------------------------------------------------------------------
      [^"]*                    any character except: '"' (0 or more
                               times (matching the most amount
                               possible))
----------------------------------------------------------------------
    )                        end of \1
----------------------------------------------------------------------
    ['"]?                    any character of: ''', '"' (optional
                             (matching the most amount possible))
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------
  (?:                      group, but do not capture (0 or more times
                           (matching the most amount possible)):
----------------------------------------------------------------------
    [^>=]                    any character except: '>', '='
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    ='                       '=\''
----------------------------------------------------------------------
    [^']*                    any character except: ''' (0 or more
                             times (matching the most amount
                             possible))
----------------------------------------------------------------------
    '                        '\''
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    ="                       '="'
----------------------------------------------------------------------
    [^"]*                    any character except: '"' (0 or more
                             times (matching the most amount
                             possible))
----------------------------------------------------------------------
    "                        '"'
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    =                        '='
----------------------------------------------------------------------
    [^'"\s]*                 any character except: ''', '"',
                             whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
  )*                       end of grouping
----------------------------------------------------------------------
  "                        '"'
----------------------------------------------------------------------
  \s?                      whitespace (\n, \r, \t, \f, and " ")
                           (optional (matching the most amount
                           possible))
----------------------------------------------------------------------
  \/?                      '/' (optional (matching the most amount
                           possible))
----------------------------------------------------------------------
  >                        '>'
----------------------------------------------------------------------