如何使用正则表达式从html字符串中获取图像URL

Question

我试图从使用正则表达式的html字符串获取我目前正在处理的是:

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]()
    }
}

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

我仍然无法从它获取图像网址,这意味着它返回我空数组.实际上我的html字符串包含一个图像.我不想使用UIWebView因为UITableView调整大小问题.所以,我需要从图像网址中取出html并使用AlamofireImage在UIImageView中显示它.

任何帮助？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"/>

至 :

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

Answer 1

描述

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

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，如果存在，则不使用引号。
• 允许属性有单引号、双引号或无引号
• 可以修改以验证任意数量的其他属性
• 避免难以解析 HTML 的困难边缘情况

例子

现场演示

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

示例文本

请注意第一行中我们正在寻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"/>

样本匹配

• 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))
----------------------------------------------------------------------
  >                        '>'
----------------------------------------------------------------------

Answer 2

这是你应该使用的正则表达式模式:

(HTTP [^\S] +(JPG | JPEG | PNG | TIFF)\ b)中

翻译:

• 查找以"http"开头的所有内容
• 不允许有空白区域
• 结束以下jpg,jpeg,png,tiff之一

正则表达式功能:

func matches(for regex: String!, in text: String!) -> [String] {    
    do {
        let regex = try RegularExpression(pattern: regex, options: [])
        let nsString = text as NSString
        let results = regex.matches(in: text, range: NSMakeRange(0, nsString.length))
        return results.map { nsString.substring(with: $0.range)}
    } catch let error as NSError {
        print("invalid regex: \(error.localizedDescription)")
        return []
    }
}

用法:

var matched = matches(for: "(http[^\\s]+(jpg|jpeg|png|tiff)\\b)", in: String(htmlStr))

注意:

• 匹配返回为具有匹配字符串对象的数组
• 此代码是为Swift 3编写的