Question

Remark: please consider XPath syntax dead here, thank you.

I have xml node (HTML actually), and I would like to get an attribute of it.

In C# (HTMLAgilityPack) I could get attribute object by name. For example having "a" node I could ask for "href" attribute.

In Scala there is "attribute" method within xml.Node, but this returns a sequence of.. nodes. An attribute is a node? How it is possible to have several attributes with the same name? I am completely puzzled.

Moreover there is xml.Attribute class but I don’t see it used in xml.Node.

I have PiS book but XML chapter is very shallow.

The question

How should I understand asking for an attribute an getting collection of nodes?

IOW: what sense is in returning an option of collection of nodes instead of returning attribute?

• option — if there is no attribute, collection should be empty, it is doubling semantics
• collection — this implies there are multiple attribute possible, so I am curious in what scenario I get collection of size > 1
• node — attribute is pretty simply entity, why such overkill and suggesting that attribute can have tree structure

Answer 1

You just want to get the value of an attribute, yes? In which case that’s pretty easy:

scala> val x = <foo this="xx" that="yy" />
x: scala.xml.Elem = <foo this="xx" that="yy"></foo>

scala> x.attribute("this")
res0: Option[Seq[scala.xml.Node]] = Some(xx)

scala> x.attribute("this").get.toString
res1: String = xx

I know that you said that you explicitly aren’t interested in XPath syntax, but in this instance it really is rather neater:

scala> x \ "@this"
res2: scala.xml.NodeSeq = xx

Having said all of this, you should be aware that there are many problems with attribute handling in Scala’s built-in XML handling. See, for example, this, this and this.