Simple question about tuple of scala
Question
I'm new to scala, and what I'm learning is tuple
.
I can define a tuple as following, and get the items:
val tuple = ("Mike", 40, "New York")
println("Name: " + tuple._1)
println("Age: " + tuple._2)
println("City: " + tuple._3)
My question is:
- How to get the length of a tuple?
- Is tuple mutable? Can I modify its items?
- Is there any other useful operation we can do on a tuple?
Thanks in advance!
Solution
1] tuple.productArity
2] No.
3] Some interesting operations you can perform on tuples: (a short REPL session)
scala> val x = (3, "hello")
x: (Int, java.lang.String) = (3,hello)
scala> x.swap
res0: (java.lang.String, Int) = (hello,3)
scala> x.toString
res1: java.lang.String = (3,hello)
scala> val y = (3, "hello")
y: (Int, java.lang.String) = (3,hello)
scala> x == y
res2: Boolean = true
scala> x.productPrefix
res3: java.lang.String = Tuple2
scala> val xi = x.productIterator
xi: Iterator[Any] = non-empty iterator
scala> while(xi.hasNext) println(xi.next)
3
hello
OTHER TIPS
One thing that you can also do with a tuple is to extract the content using the match
expression:
def tupleview( tup: Any ){
tup match {
case (a: String, b: String) =>
println("A pair of strings: "+a + " "+ b)
case (a: Int, b: Int, c: Int) =>
println("A triplet of ints: "+a + " "+ b + " " +c)
case _ => println("Unknown")
}
}
tupleview( ("Hello", "Freewind"))
tupleview( (1,2,3))
Gives:
A pair of strings: Hello Freewind
A triplet of ints: 1 2 3
Tuples
are immutable, but, like all cases classes, they have a copy method that can be used to create a new Tuple
with a few changed elements:
scala> (1, false, "two")
res0: (Int, Boolean, java.lang.String) = (1,false,two)
scala> res0.copy(_2 = true)
res1: (Int, Boolean, java.lang.String) = (1,true,two)
scala> res1.copy(_1 = 1f)
res2: (Float, Boolean, java.lang.String) = (1.0,true,two)
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