使用正则表达式或替代方法快速抓取网页

Question

首先查看下面的更新。

我正在尝试为 reddit 上的指定子 reddit 抓取所有版主。 API 只允许您获取子 reddit 的所有版主用户名，因此最初我已经获取了所有这些用户名，然后对这些配置文件中的每一个执行了额外的请求以获取头像 url。这最终超出了 API 限制。

因此，我只想获取下一页的来源并在收集每个页面上的 10 个用户名和头像 url 的同时进行分页。这将最终以更少的请求轮询网站。我了解如何进行分页部分，但现在我正在尝试了解如何收集用户名和相邻的头像 URL。

所以采取以下网址：

https://www.reddit.com/r/videos/about/moderators/

所以我会拉取整个页面源码，

将所有模组用户名和网址添加到模组对象中，然后添加到数组中。

在我返回的字符串上使用正则表达式是个好主意吗？

这是我目前的代码，任何帮助都会很棒：

    func tester() {
       let url = URL(string: "https://www.reddit.com/r/videos/about/moderators")!

       let task = URLSession.shared.dataTask(with: url) { data, response, error in
           guard let data = data, error == nil else {
               print("\(error)")
               return
           }

        let string = String(data: data, encoding: .utf8)

            let regexUsernames = try? NSRegularExpression(pattern: "href=\"/user/[a-z0-9]\"", options: .caseInsensitive)

            var results = regexUsernames?.matches(in: string as String, options: [], range: NSRange(location: 0, length: string.length))

            let regexProfileURLs = try? NSRegularExpression(pattern: "><img src=\"[a-z0-9]\" style", options: .caseInsensitive)

           print("\(results)") // This shows as empty array
       }

       task.resume()
   }

我也尝试了以下方法，但收到此错误：

Can't form Range with upperBound < lowerBound

代码：

    func tester() {
       let url = URL(string: "https://www.reddit.com/r/videos/about/moderators")!

       let task = URLSession.shared.dataTask(with: url) { data, response, error in
           guard let data = data, error == nil else {
            print("data was nil")
               return
           }

        guard let htmlString = String(data: data, encoding: .utf8) else {
            print("cannot cast data into string")
            return
        }

        let leftSideOfValue = "href=\"/user/"
        let rightSideOfValue = "\""

        guard let leftRange = htmlString.range(of: leftSideOfValue) else {
            print("cannot find range left")
            return
        }

        guard let rightRange = htmlString.range(of: rightSideOfValue) else {
            print("cannot find range right")
            return
        }

        let rangeOfTheValue = leftRange.upperBound..<rightRange.lowerBound

        print(htmlString[rangeOfTheValue])
}

更新：

所以我已经到了它会给我第一个用户名的地步，但是我正在循环并且一遍又一遍地得到相同的用户名。推进每个增量步骤的最佳方式是什么？有没有办法让 newHTMLString = htmlString.dropFirst(k: ?) 用我们刚刚得到的元素之后的子字符串替换 htmlString？

func tester() {
       let url = URL(string: "https://www.reddit.com/r/pics/about/moderators")!

       let task = URLSession.shared.dataTask(with: url) { data, response, error in
           guard let data = data, error == nil else {
            print("data was nil")
               return
           }

        guard let htmlString = String(data: data, encoding: .utf8) else {
            print("cannot cast data into string")
            return
        }


        let counter =  htmlString.components(separatedBy:"href=\"/user/")
        let count = counter.count

        for  i in 0...count {

            let leftSideOfUsernameValue = "href=\"/user/"
            let rightSideOfUsernameValue = "\""

            let leftSideOfAvatarURLValue = "><img src=\""
            let rightSideOfAvatarURLValue = "\">"


          guard let leftRange = htmlString.range(of: leftSideOfUsernameValue) else {
                print("cannot find range left")
                return
            }

            guard let rightRange = htmlString.range(of: rightSideOfUsernameValue) else {
                print("cannot find range right")
                return
            }

            let username = htmlString.slice(from: leftSideOfUsernameValue, to: rightSideOfUsernameValue)
            print(username)
            guard let avatarURL = htmlString.slice(from: leftSideOfAvatarURLValue, to: rightSideOfAvatarURLValue) else {
                print("Error")
                return
            }
            print(avatarURL)

        }

       }

       task.resume()
   }

我也试过了：

           let endString = String(avatarURL + rightSideOfAvatarURLValue)
            let endIndex = htmlString.index(endString.endIndex, offsetBy: 0)
            let substringer = htmlString[endIndex...]
            htmlString = String(substringer)

Answer 1

您应该能够通过执行以下操作调用简单的正则表达式将所有名称和网址拉入两个单独的数组：

func tester() {
    let url = URL(string: "https://www.reddit.com/r/pics/about/moderators")!

    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data, error == nil else { return }
        guard let htmlString = String(data: data, encoding: .utf8) else { return }

        let names = htmlString.matching(regex: "href=\"/user/(.*?)\"")
        let imageUrls = htmlString.matching(regex: "><img src=\"(.*?)\" style")
        print(names)
        print(imageUrls)
    }
    task.resume()
}

extension String {
    func matching(regex: String) -> [String] {
        guard let regex = try? NSRegularExpression(pattern: regex, options: []) else { return [] }
        let result  = regex.matches(in: self, options: [], range: NSMakeRange(0, self.count))
        return result.map {
            return String(self[Range($0.range, in: self)!])
        }
    }
}

或者您可以为每个<div class="_1sIhmckJjyRyuR_z7M5kbI"> 创建一个对象，然后根据需要获取要使用的名称和网址。