CODEWITHSUNDEEP
scalaiterable
zbstof
zbstof

Reputation: 1072

Trying to append to Iterable[String]

I'm trying to add another string to Iterable[String] for easy concatenation, but the result is not what I expect.

scala> val s: Iterable[String] = "one string" :: "two string" :: Nil
s: Iterable[String] = List(one string, two string)

scala> s.mkString(";\n")
res3: String =
one string;
two string

scala> (s ++ "three").mkString(";\n")
res5: String =
one string;
two string;
t;
h;
r;
e;
e

How should I should I rewrite this snippet to have 3 string in my iterable?

Edit: I should add, that order of items should be preserved

Upvotes: 4

Views: 15367

Answers (3)

Joerg Schmuecker
Joerg Schmuecker

Reputation: 111

I like to use toBuffer and then +=

scala> val l : Iterable[Int] = List(1,2,3)
l: Iterable[Int] = List(1, 2, 3)

scala> val e : Iterable[Int] = l.toBuffer += 4
e: Iterable[Int] = ArrayBuffer(1, 2, 3, 4)

or in your example:

scala> (s.toBuffer += "three").mkString("\n")

I have no idea why this operation isn't supported in the standard library. You can also use toArray but if you add more than one element this will be less performant - I would assume - as the buffer should return itself if it another element is added.

Upvotes: 0

senia
senia

Reputation: 38045

++ is for collection aggregation. There is no method +, :+ or add in Iterable, but you can use method ++ like this:

scala> (s ++ Seq("three")).mkString(";\n")
res3: String =
one string;
two string;
three

Upvotes: 8

mguillermin
mguillermin

Reputation: 4181

The ++ function is waiting for a Traversable argument. If you use just "three", it will convert the String "three" to a list of characters and append every character to s. That's why you get this result.

Instead, you can wrap "three" in an Iterable and the concatenation should work correctly : 

scala> (s ++ Iterable[String]("three")).mkString(";\n")
res6: String =
one string;
two string;
three

Upvotes: 5

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