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swift - 使用正则表达式或替代方法快速抓取网页

问题描述

先看下面的更新。

我正在尝试在 reddit 上为指定的子 reddit 抓取所有版主。API 仅允许您获取子 reddit 的所有版主用户名，因此最初我已获取所有这些用户名，然后对每个配置文件执行额外请求以获取头像 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页上的 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 mods 用户名和 url 添加到 mod 对象中，然后添加到数组中。

在我回来的字符串上使用正则表达式是个好主意吗？

到目前为止，这是我的代码，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()
   }

我也尝试了以下但得到这个错误：

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？有没有办法像 let 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：

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

标签： swiftregexweb-scrapingswift3

解决方案

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

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