Retrieving Array of Links with regex - Swift

Question

I am trying to parse an html page that contains these values:

<a href="somesite.html?id=123">...</a>
<a href="somesite.html?id=456">...</a>
<a href="somesite.html?id=789">...</a>
<a href="anothersite.html">...</a>

How would I parse the Html String to get back an array of where it only contains the somesite.html:

["somesite.html?id=123", "somesite.html?id=456", "somesite.html?id=456"]

Edited

Using Zhiguo Wang's base answer, I can't seem to get only the somesite.html id values... The 3rd item in the array contains excess characters:

let htmlString = "<a href=\"somesite.html?id=123\">...</a>" +
"<a href=\"somesite.html?id=456\">...</a>" +
"<a href=\"somesite.html?id=789\">...</a>" +
"<a href=\"anothersite.html\">...</a>\""
let seperateComponent = "<a href=\"somesite.html?id="

let linkExp = "[\\w\\W]*\">"

Returns this value:

["123", "456", "789\\">...</a><a href=\\"anothersite.html"]

Expected Value: ["123", "456", "789"]

...hmm. Changing linkExp to the below resolves it. What does \W represent in Regex?

let linkExp = "[\\w]*\">"

..The length is wrong. Casted to NSString to grabbed the proper length.

Edited 2

It looks like if this string comes first before the somesite, then it includes Origin in the array:

<meta name=\"referrer\" content=\"origin\">

@Wongzigii I feel like there's an easier solution than a 3rd party library. E.g all those a tags contain the same format of "somesite.html?id=". Can't regex do a find on those first characters up until the id=, then stop at the first double quotes? Idk how that would look though — Tim Nuwin
– Tim Nuwin, Commented Sep 22, 2015 at 4:18

Zhiguo Wang · Accepted Answer · 2015-09-22 05:34:16Z

1

talk is cheap, show me the code

    let htmlString = "<a href=\"somesite.html?id=123\">...</a><a href=\"somesite.html?id=456\">...</a><a href=\"somesite.html?id=789\">...</a>"
    let seperateComponent = "<a href=\""

    let linkExp = "[\\w\\W]*\">"
    let linkRegExp = NSRegularExpression(pattern:linkExp, options: NSRegularExpressionOptions.CaseInsensitive, error: nil)
    let seperatedArray = htmlString.componentsSeparatedByString(seperateComponent)
    var resultArray = [String]()

    if seperatedArray.count > 1 {
        for seperatedString in seperatedArray {
            if seperatedString.lengthOfBytesUsingEncoding(NSUTF8StringEncoding) > 3{
                let myRange = linkRegExp!.rangeOfFirstMatchInString(seperatedString, options:NSMatchingOptions.ReportCompletion, range: NSMakeRange(0, seperatedString.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)))
                if myRange.location != NSNotFound {
                    let matchString = (seperatedString as NSString).substringWithRange(myRange)
                    let linkString = (matchString as NSString).substringToIndex(matchString.lengthOfBytesUsingEncoding(NSUTF8StringEncoding) - 2)

                    resultArray.append(linkString)
                }
            }
        }
    }

    println(resultArray)

these codes have been run on xcode 6.4 and the result is right.sorry " i need at least 10 reputation to post images" so result pic won't be posted here.

edited Sep 22, 2015 at 5:34

answered Sep 22, 2015 at 5:20

Zhiguo Wang

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5 Comments

Martin R Over a year ago

Note that this will crash if the input string contains multiple non-ASCII characters like "ÄÖÜ" or "€". The reason is that counting UTF-8 bytes is not the right method to compute an NSRange. Compare e.g. stackoverflow.com/questions/27880650/….

Tim Nuwin Over a year ago

Thanks Zhiguo, I have updated the question to handle one last test case.

Tim Nuwin Over a year ago

I can't seem to get it to work if i set the separatorComponent to: let seperateComponent = "<a href=\"somesite.html?id=" It includes the other link values.

Zhiguo Wang Over a year ago

Thanks Martin R,that's really a serious situation that i've never thought about.

Zhiguo Wang Over a year ago

And @TimNuwin i know your problem now ,and i'm glad to help 1.\W stands for all the capital characters from A to Z and numbers and other common symbols. 2.if you let seperateComponent = "<a href=\"somesite.html?id=" it won't be right because you separate the last two link together into the same string. 3.sorry i realized that i spelled wrong "separate" :D 4.improved code will be shown below

Community · Accepted Answer · 2017-05-23 11:44:29Z

0

I think regular expression may go for a toss while parsing HTML files. You have better way of parsing HTML files the iOS way. Here is a tutorial on this. TFHpple and NDHpple are your friends here.

Here is a related SO thread.

edited May 23, 2017 at 11:44

CommunityBot

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answered Sep 22, 2015 at 4:35

Abhinav

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Comments

Zhiguo Wang · Accepted Answer · 2015-09-25 09:29:14Z

here's the improved code

    let htmlString = "<a href=\"somesite.html?id=123\">...</a>" +
        "<a href=\"somesite.html?id=456\">...</a>" +
        "<a href=\"somesite.html?id=789\">...</a>" +
    "<a href=\"anothersite.html\">...</a>\""
    let seperateComponent = "<a href=\""

    let linkExp = "[\\w\\W]*\">"
    let linkRegExp = NSRegularExpression(pattern:linkExp, options: NSRegularExpressionOptions.CaseInsensitive, error: nil)
    let seperatedArray = htmlString.componentsSeparatedByString(seperateComponent)
    var resultArray = [String]()

    if seperatedArray.count > 1 {
        for seperatedString in seperatedArray {
            if seperatedString.lengthOfBytesUsingEncoding(NSUTF8StringEncoding) > 3{
                let myRange = linkRegExp!.rangeOfFirstMatchInString(seperatedString, options:NSMatchingOptions.ReportCompletion, range: NSMakeRange(0, seperatedString.lengthOfBytesUsingEncoding(NSUTF8StringEncoding)))
                if myRange.location != NSNotFound {
                    let matchString = (seperatedString as NSString).substringWithRange(myRange)

                    let linkWished = "somesite.html?id="

                    if matchString.componentsSeparatedByString(linkWished).count > 1{

                        var linkString = (matchString as NSString).substringFromIndex(linkWished.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))

                        linkString = (linkString as NSString).substringToIndex(linkString.lengthOfBytesUsingEncoding(NSUTF8StringEncoding) - 2)

                        resultArray.append(linkString)
                    }


                }
            }
        }
    }

    println(resultArray)

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