CODEWITHSUNDEEP
erlangelixir
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NoDisplayName

Reputation: 15746

Removing elements with XPath

So let's say I have an XML file and I want to remove some nodes from it using their XPath. How would I do that and is it possible in the first place with xmerl or erlsom or maybe something else?

And if there is not a simple way with XPath, what is the correct way to remove elements from XML in general?

Upvotes: 2

Views: 774

Answers (1)

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121010

As stated by W3C,

XPath is a language for addressing parts of an XML document

the above literally means XPath is to query XML, not to modify it. The common approach to modifying XML document, would be to one of those:

  • using XSLT transformation schema;
  • reading the content into memory, modifying it and saving it back to the file.

AFAIU, the former is out of the scope of this question. For the latter, one might use Exsom library, which is “an Elixir wrapper around the erlsom XML parsing library.”

Assuming we have the xml and xsd taken from Excom examples:

<?xml version="1.0" encoding="UTF-8"?>
<foo attr="yo">
  <bar>1</bar>
  <bar>2</bar>
</foo>

One might do something like this to delete second bar node (most of the code is taken as is from Excom tests:

{ :ok, model } = Exsom.XSD.File.parse("complex.xsd")
{ :ok, instance, _ } = Exsom.File.parse("complex.xml", model)
#⇒ {:ok, {:foo_type, [], 'yo', ['1', '2']}}

Modify it according to what you want, e.g. remove bar element with 2

instance = {:foo_type, [], 'yo', ['1']}
{ :ok, binary_xml } = Exsom.compose(instance, model, [{ :output, :binary }])
#⇒ {:ok, "<foo attr=\"yo\"><bar>1</bar></foo>"}

Now you might write the binary_xml to a file.

Upvotes: 2

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