[erlang-questions] xmerl and selecting attributes

[Robert Raschke]

On Tue, Sep 8, 2009 at 11:21 AM, Ralf Doering <rdoering@REDACTED> wrote:

>
> Hello,
>
> seems I've got a problem selecting the value of an attribute from an XML
> tag.
>
> Consider the following short example:
>
> --8<---------------cut here---------------start------------->8---
> -module(xmerl_test).
>
> -include_lib("xmerl/include/xmerl.hrl").
>
> -import(xmerl_xs,
>        [ xslapply/2, value_of/1, select/2, built_in_rules/2 ]).
>
>
> -export([start/0]).
>
> start() ->
>    {XmlElement, _Rest} = xmerl_scan:string("<test myattr=\"123\" />"),
>    template(XmlElement).
>
>
> template( E = #xmlElement{name='test'}) ->
>    Attr = value_of(select("@myattr", E)),
>    io:format("MyAttribute: ~w~n", [Attr]),
>    xslapply(fun template/1,E),
>    E;
>
> template(E) ->
>    built_in_rules( fun template/1, E).
>
> --8<---------------cut here---------------end--------------->8---
>
>
> When running this, I get:
>
> (emacs@REDACTED)13> xmerl_test:start().
> MyAttribute: []
> []
>
> I was expecting that value_of(select("@myattr"),E) would extract "123" as
> attribute value. Am I wrong here, do I use the wrong XPath for this?
>
>
I think the xmerl_xs:value_of/1 function will only ever return the text
nodes of the element list you supply.

The xmerl_xs:select/2 invocation you have is fine:

Erlang (BEAM) emulator version 5.6.5 [smp:2] [async-threads:0]

Eshell V5.6.5  (abort with ^G)
1> rr(xmerl).
[xmerl_event,xmerl_fun_states,xmerl_scanner,xmlAttribute,
 xmlComment,xmlContext,xmlDecl,xmlDocument,xmlElement,
 xmlNamespace,xmlNode,xmlNsNode,xmlObj,xmlPI,xmlText]
2> {E,_} = xmerl_scan:string("<test myattr=\"123\" />").
{#xmlElement{
     name = test,expanded_name = test,nsinfo = [],
     namespace = #xmlNamespace{default = [],nodes = []},
     parents = [],pos = 1,
     attributes =
         [#xmlAttribute{
              name = myattr,expanded_name = [],nsinfo = [],namespace = [],
              parents = [],pos = 1,language = [],value = "123",
              normalized = false}],
     content = [],language = [],xmlbase = "C:/Robby",
     elementdef = undeclared},
 []}
3> xmerl_xs:select("@myattr", E).
[#xmlAttribute{name = myattr,expanded_name = [],nsinfo = [],
               namespace = [],parents = [],pos = 1,language = [],
               value = "123",normalized = false}]


So, I guess you have to get the value through the record itself.

Robby