(root)
(record id="1")
(fld1)Harry(/fld1)
(fld2)Ron(/fld2)
(/record)
(record id="2")
(fld1)Fred(/fld1)
(fld2)George(/fld2)
(/record)
(/root)The two main functions for parsing XML are revCreateXMLTree, which takes the XML source as a parameter, and revCreateXMLTreeFromFile, which gets the XML from a file. Besides the source, there are three other parameters, all boolean switches. The first switch is whether to bail or not if an error in syntax occurs; the second is whether you want the function to build a tree in memory for you and return a pointer to it; the last is whether you want messages sent as the parsing proceeds. You'll want to set one of the last two switches true or the function will only tell you whether there was an error in syntax.
There are basically two ways to use these functions, controlled by the last two switches: create a tree in memory and then use the other rev-XML functions to traverse and interrogate it; or have the parser send messages as it goes, like revStartXMLNode, revStartXMLData, etc. Here is what I found out.
1. The TD says that revStartXMLTree and revEndXMLTree messages will be sent when the parsing begins and ends; they are not. I noticed a reference in the "See Also" menu to "revXMLStartTree" but no entry for it, so on a hunch I tried that and it worked: the functions (Rev 2.1.2) send revXMLStartTree and revXMLEndTree. I filed this as a documentation bug (#1165), but probably they meant to change the names as the docs say; guess they will sort it all out.
2. There is a difference in the messages sent depending on if you also create the tree. I put simple handlers similar to this for all the messages:
on revStartXMLNode attr put "start node" && attr & return after msg end revStartXMLNode
Here is the sort of thing we get from either function with create_tree false and send_messages true:
start tree: start node: root start data:
start node: record start data:
start node: fld1 start data: Harry end node fld1 start data:
start node: fld2 start data: Ron end node fld2 start data:
end node record ....
But with create_tree true and send_messages true we get the much cleaner:
start tree: start node: root start node: record start node: fld1 start data: Harry end node fld1 start node: fld2 start data: Ron end node fld2 end node record ....
Obviously this is not a big problem, but it just don't seem right. I don't need the tree, but I wish I didn't have to deal with extra start data messages....
3. The TD says the message "revStartXMLnode nodeAttributes" will get sent when the parser encounters an opening tag, where nodeAttributes "is a string containing the attributes of the XML element currently being parsed, one attribute per line." The reason I started playing with this is because this doesn't make clear how you would know what the tag is. Notice in the test source above that when (record id="1") is parsed the parameter sent with the start node message is just the tag, "record". Where's the id attribute? I didn't write a bug report about this because I'm not sure I understand how it's supposed to work.
So can anyone provide any help, understanding, advice, or warnings about any of this? Thanks, and sorry for the long message.
Jim Lyons
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