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47 lines
1.7 KiB
Plaintext
47 lines
1.7 KiB
Plaintext
// use case in function args for pattern matching.
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(xs zip ys) map { case (x,y) => x*y } // GOOD
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(xs zip ys) map( (x,y) => x*y ) // BAD
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// "v42" is interpreted as a name matching any Int value, and "42" is printed.
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// BAD
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val v42 = 42
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Some(3) match {
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case Some(v42) => println("42")
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case _ => println("Not 42")
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}
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// "`v42`" with backticks is interpreted as the existing val v42, and “Not 42” is printed.
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// GOOD
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val v42 = 42
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Some(3) match {
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case Some(`v42`) => println("42")
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case _ => println("Not 42")
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}
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// UppercaseVal is treated as an existing val, rather than a new pattern variable, because it starts with an uppercase letter.
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// Thus, the value contained within UppercaseVal is checked against 3, and “Not 42” is printed.
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// GOOD
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val UppercaseVal = 42
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Some(3) match {
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case Some(UppercaseVal) => println("42")
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case _ => println("Not 42")
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}
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// Creating an alias for a match
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// This will maintain the original value passed into the match function, using the '@' symbol, and print "Matched Some(3)"
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Some(3) match {
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case foundSome @ Some(_) => println("Matched " + foundSome)
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case _ => println("Matched nothing")
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}
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// Case Classes
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// This method allows you to match on any combination of properties of a case class
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case class Example(a: Int, b: String, c: Boolean)
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Example(1, "word", true) match {
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case Example(3, _, _) => println("Matches any Example where a = 3")
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case Example(_, "foo", _) => println("Matches any Example where b = foo")
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case Example(_, _, false) => println("Matches any Example where c = false")
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case Example(1, "word", true) => println("Matches our Example")
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case Example(_, _, _) => println("Matches any other Example")
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}
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