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regular-expression-patterns.md

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Regular Expression Patterns
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/tutorials/tour/regular-expression-patterns.html

Regular expressions are strings which can be used to find patterns (or lack thereof) in data. Any string can be converted to a regular expression using the .r method.

{% tabs regex-patterns_numberPattern class=tabs-scala-version %}

{% tab 'Scala 2' for=regex-patterns_numberPattern %}

importscala.util.matching.RegexvalnumberPattern:Regex="[0-9]".r numberPattern.findFirstMatchIn("awesomepassword") match { caseSome(_) => println("Password OK") caseNone=> println("Password must contain a number") }

{% endtab %}

{% tab 'Scala 3' for=regex-patterns_numberPattern %}

importscala.util.matching.RegexvalnumberPattern:Regex="[0-9]".r numberPattern.findFirstMatchIn("awesomepassword") matchcaseSome(_) => println("Password OK") caseNone=> println("Password must contain a number")

{% endtab %}

{% endtabs %}

In the above example, the numberPattern is a Regex (regular expression) which we use to make sure a password contains a number.

You can also search for groups of regular expressions using parentheses.

{% tabs regex-patterns_keyValPattern class=tabs-scala-version %}

{% tab 'Scala 2' for=regex-patterns_keyValPattern %}

importscala.util.matching.RegexvalkeyValPattern:Regex="([0-9a-zA-Z- ]+): ([0-9a-zA-Z-#()/. ]+)".r valinput:String="""background-color: #A03300; |background-image: url(img/header100.png); |background-position: top center; |background-repeat: repeat-x; |background-size: 2160px 108px; |margin: 0; |height: 108px; |width: 100%;""".stripMargin for (patternMatch <- keyValPattern.findAllMatchIn(input)) println(s"key: ${patternMatch.group(1)} value: ${patternMatch.group(2)}")

{% endtab %}

{% tab 'Scala 3' for=regex-patterns_keyValPattern %}

importscala.util.matching.RegexvalkeyValPattern:Regex="([0-9a-zA-Z- ]+): ([0-9a-zA-Z-#()/. ]+)".r valinput:String="""background-color: #A03300; |background-image: url(img/header100.png); |background-position: top center; |background-repeat: repeat-x; |background-size: 2160px 108px; |margin: 0; |height: 108px; |width: 100%;""".stripMargin for patternMatch <- keyValPattern.findAllMatchIn(input) do println(s"key: ${patternMatch.group(1)} value: ${patternMatch.group(2)}")

{% endtab %}

{% endtabs %}

Here we parse out the keys and values of a String. Each match has a group of sub-matches. Here is the output:

key: background-color value: #A03300 key: background-image value: url(img/header100.png) key: background-position value: top center key: background-repeat value: repeat-x key: background-size value: 2160px 108px key: margin value: 0 key: height value: 108px key: width value: 100

Moreover, regular expressions can be used as patterns (in match expressions) to conveniently extract the matched groups:

{% tabs regex-patterns_saveContactInformation class=tabs-scala-version %}

{% tab 'Scala 2' for=regex-patterns_saveContactInformation %}

defsaveContactInformation(contact: String):Unit= { importscala.util.matching.RegexvalemailPattern:Regex="""^(\w+)@(\w+(.\w+)+)$""".r valphonePattern:Regex="""^(\d{3}-\d{3}-\d{4})$""".r contact match { case emailPattern(localPart, domainName, _) => println(s"Hi $localPart, we have saved your email address.") case phonePattern(phoneNumber) => println(s"Hi, we have saved your phone number $phoneNumber.") case _ => println("Invalid contact information, neither an email address nor phone number.") } } saveContactInformation("123-456-7890") saveContactInformation("JohnSmith@sample.domain.com") saveContactInformation("2 Franklin St, Mars, Milky Way")

{% endtab %}

{% tab 'Scala 3' for=regex-patterns_saveContactInformation %}

defsaveContactInformation(contact: String):Unit=importscala.util.matching.RegexvalemailPattern:Regex="""^(\w+)@(\w+(.\w+)+)$""".r valphonePattern:Regex="""^(\d{3}-\d{3}-\d{4})$""".r contact matchcase emailPattern(localPart, domainName, _) => println(s"Hi $localPart, we have saved your email address.") case phonePattern(phoneNumber) => println(s"Hi, we have saved your phone number $phoneNumber.") case _ => println("Invalid contact information, neither an email address nor phone number.") saveContactInformation("123-456-7890") saveContactInformation("JohnSmith@sample.domain.com") saveContactInformation("2 Franklin St, Mars, Milky Way")

{% endtab %}

{% endtabs %}

The output would be:

Hi, we have saved your phone number 123-456-7890. Hi JohnSmith, we have saved your email address. Invalid contact information, neither an email address nor phone number.
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