Append Map[String, String] to a Seq[Map[String, String]] - scala

Question

This drives me crazy, I can't figure out why this gives me an error.
Here an example of my code:
var seqOfObjects:Seq[Map[String, String]] = Seq[Map[String, String]]()
for(item <- somelist) {
seqOfObjects += Map(
"objectid" -> item(0).toString,
"category" -> item(1),
"name" -> item(2),
"url" -> item(3),
"owneremail" -> item(4),
"number" -> item(5).toString)
}
This gives me an error saying:
Type mismatch, expected: String, actual: Map[String, String]
But a Map[String, String] is exactly what I want to append into my Seq[Map[String, String]].
Why is it saying that my variable seqOfObjects expects a String??
Anyone have a clue?
Thanks

Answer 1

a += b means a = a.+(b). See this answer.
There is no method + in Seq, so you can't use +=.
scala> Seq[Int]() + 1
<console>:8: error: type mismatch;
found : Int(1)
required: String
Seq[Int]() + 1
^
required: String is from string concatenation. This behavior is inherited from Java:
scala> List(1, 2, 3) + "str"
res0: String = List(1, 2, 3)str
Actually method + here is from StringAdd wrapper. See implicit method Predef.any2stringadd.
You could use :+= or +:= instead of +=.
Default implementation of Seq is List, so you should use +: and +:= instead of :+ and :+=. See Performance Characteristics of scala collections.
You could also use List instead of Seq. There is :: method in List, so you can use ::=:
var listOfInts = List[Int]()
listOfInts ::= 1
You can rewrite your code without mutable variables using map:
val seqOfObjects =
for(item <- somelist) // somelist.reverse to reverse order
yield Map(...)
To reverse elements order you could use reverse method.

Answer 2

Short foldLeft example:
sl.foldLeft(Seq[Map[Srting, String]]()){ (acc, item) => Map(/* map from item */) +: acc }