CODEWITHSUNDEEP
scalaforeacharraybuffer
Mikkel
Mikkel

Reputation: 318

Weird behavior while iterating over ArrayBuffer

I have two ArrayBuffers, the first (A) is a subset of the other and only contains long IDs. The second (B) contains objects of a case class g which has the ID as an attribute. Now I want to loop over A in order to remove all objects in B matching the corresponding ID as well as the ID from A. I use the following method

def removeID (ID:Long) {
  B.find(_.ID == ID) match {
    case Some(s) => 
      B.remove(B.indexWhere(_.ID == ID))
      A -= ID

   case None => sys.error("Cannot remove ID $ID")
}

}

I'm a little bit confused since the error I get now is:

java.lang.RuntimeException: Cannot remove ID 0

which does not make sense since there is no 0 in A or B. I tried to figure out what exactly happens during the loop it is obvious that

for(ID <- A) {removeID(ID)}

just applies the removeID method on every 2nd element until it reaches the end of A and then tries to find the ID 0 which does not exists.

Does somebody know where this behavior comes from?

Edit: So the problem is not the removal of an ID (it happens like it should) but rather the iteration over the ArrayBuffer which does not make sense.

Upvotes: 0

Views: 308

Answers (1)

Tesseract
Tesseract

Reputation: 8139

You probably get that error because there is no ID 0. So the case None part gets executed. But I suggest you use filter instead.

def removeID(ID: Long) {
  B = B.filterNot(_.ID == ID)
  A -= ID
}

Upvotes: 0

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