Generic xml traversal.

Brian Lonsdorf <>
Thu Aug 19 19:04:58 CEST 2010


I apologize if this is a repost for some, I think I posted it in some old buried thread by accident yesterday.

Hi everyone!  I'm very excited to be starting my erlang journey, but I've been stuck on this for a few days now.

I'm trying to create key, value pair tuples out of xml.  I'd like to make a list out of nested xml too.  For instance:
<something>
	<Item>
		<name>The Name!</name>
		<reviews>
				<review>
					<review-by>WE</review-by>
					<review-points>92</review-points>
				</review>
			
				<review>
					<review-by>WS</review-by>
					<review-points>90</review-points>
				</review>
		</reviews>
	</Item>
</something>

Should turn out like:

[{"name", "The Name!"}, {"reviews", [{"review-by", "WE"}, {"review-points", 92}], {"review-by", "WS"}, {"review-points", 90}]} ]

Where Item is my main node that i want to get lists of.

I've admittedly cargo culted and tweaked the code below.  It only returns a list of the first Item's elements.  And I'm not sure how to begin the nested ones.

Thanks so much!

-Brian
-----------------------------

-module(reader).
-compile(export_all).
-include_lib("xmerl/include/xmerl.hrl").

parse(FileName) ->
	{Records,_} = xmerl_scan:file(FileName),
	extract(Records, []).
		
extract(Record, Acc) when is_record(Record, xmlElement) ->
	case Record#xmlElement.name of
		'Item' ->
		 	ItemData = lists:foldl(fun extract/2, [], Record#xmlElement.content),
		 	[ {item, ItemData} | Acc ];
		_ ->
			lists:foldl(fun extract/2, Acc, Record#xmlElement.content)
	end;
	
extract({xmlText, [{Attribute, _}, {'Item', 2}, _], _, _, Value, text}, Acc) ->
	[{Attribute, Value}|Acc];
		
extract(_, Acc) ->
	Acc.

-------------------------------

I've also seen this done with list comprehension.  It's beautiful, but i can't get it to nest:

parse(FileName) ->
    {#xmlElement{content=Item}, _} = xmerl_scan:file(FileName),
    [{Tag, Val} ||
        #xmlElement{content=Query} <- Item,
        #xmlElement{content=Fields} <- Query,
        #xmlText{parents=[{Tag, _} | _], value=Val} <- Fields].



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