append xml node if it not present in the list

Question

I have block of code:

object XmlExample {

  def main(args: Array[String]): Unit = {
    val someXml = 
     <books>
      <book title="The Woman in White">
        <author>Wilkie Collins</author>
      </book> <book title="Great Expectations">
        <author>Charles Dickens</author>
      </book>
    </books>
    println("The xml object is of type: " + someXml.child)


  }

}

I want check if node <c1>does not exist as its child, then I added it like <c1>Null</c1>

Answer 1

I'm not sure to have fully understood does not exist as its child ... or what you exactly mean by I added it but here's my straight answer for adding optionally a direct child of books :

def addC1IfNotHere(someXml: scala.xml.Elem) = (someXml \ "c1") match {
  case Seq() =>
    someXml.copy(child = <c1>Null</c1> +: someXml.child)
  case _ => someXml
}

this works like:

val someXmlWithC1 = 
<books>
   <c1>anything else</c1>
   <book title="The Woman in White">
    <author>Wilkie Collins</author>
   </book> <book title="Great Expectations">
    <author>Charles Dickens</author>
  </book>
</books>
val someXmlWithoutC1 = 
<books>
   <book title="The Woman in White">
    <author>Wilkie Collins</author>
   </book> <book title="Great Expectations">
    <author>Charles Dickens</author>
  </book>
</books>
val hasItsOriginalC1 = addC1IfNotHere(someXmlWithC1)
val hasANewC1 = addC1IfNotHere(someXmlWithoutC1)
println(hasItsOriginalC1)
println(hasANewC1)

should normally print:

<books>
   <c1>anything else</c1>
   <book title="The Woman in White">
    <author>Wilkie Collins</author>
   </book> <book title="Great Expectations">
    <author>Charles Dickens</author>
  </book>
</books>
<books><c1>Null</c1>
   <book title="The Woman in White">
    <author>Wilkie Collins</author>
   </book> <book title="Great Expectations">
    <author>Charles Dickens</author>
  </book>
</books>

Hope it helps. Don't hesitate whenever c1 isn't at the place you expected or something else.