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This article mainly introduces the relevant knowledge of Scala extractor case analysis, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this Scala extractor case analysis article. Let's take a look at it.

The Scala extractor is an object with a unapply method. The unapply method is the reverse operation of the apply method: unapply takes an object and then extracts the value from the object, which is usually used to construct the value of the object.

The following example demonstrates the extractor object for an email address:

Object Test {def main (args: Array [String]) {println ("Apply method:" + apply ("Zara", "gmail.com")); println ("Unapply method:" + unapply ("Zara@gmail.com")); println ("Unapply method:" + unapply ("Zara Ali")) } / / injection method (optional) def apply (user: String, domain: String) = {user + "@" + domain} / / extraction method (required) def unapply (str: String): Option [(String, String)] = {val parts = str split "@" if (parts.length = 2) {Some (parts (0), parts (1))} else {None}

Execute the above code, and the output is as follows:

$scalac Test.scala$ scala TestApply method: Zara@gmail.comUnapply method: Some ((Zara,gmail.com)) Unapply method: None

The above object defines two methods: the apply and unapply methods. With the apply method, we can create objects without using the new operation. So you can construct a string "Zara@gmail.com" by saying Test ("Zara", "gmail.com").

The unapply method is the reverse operation of the apply method: unapply takes an object and then extracts the value from the object, which is usually used to construct the value of the object. In the example, we use the Unapply method to extract the suffix of the user name and e-mail address from the object.

The unapply method in the instance returns None if the string passed in is not a mailbox address. The code is demonstrated as follows:

Unapply ("Zara@gmail.com") equals Some ("Zara", "gmail.com") unapply ("Zara Ali") equals None

Extractor uses pattern matching

When we instantiate a class, we can take 0 or more arguments, and the compiler will call the apply method when instantiating. We can define apply methods in both classes and objects.

As we mentioned earlier, unapply is used to extract the value we specified to find, which is the opposite of what apply does. When we use the match statement in the extractor object, the unapply executes automatically, as follows:

Object Test {def main (args: Array [String]) {val x = Test (5) println (x) x match {case Test (num) = > println (x + "is twice as much as" + num + "!) / / unapply is called case _ = > println ("unable to calculate")}} def apply (x: Int) = xint2 def unapply (z: Int): Option [Int] = if (z% 2 calculation 0) Some (zstroke 2) else None}

Execute the above code, and the output is as follows:

$scalac Test.scala$ scala Test1010 is twice as much as 5! This is the end of the article on "case Analysis of the use of Scala extractors". Thank you for reading! I believe you all have a certain understanding of the knowledge of "case analysis of the use of Scala extractors". If you want to learn more, you are welcome to follow the industry information channel.

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