Examples
The code excerpt below creates a parser with 2 callbacks and feeds a test string to it. The parsing of the test string triggers the callbacks, printing the results.
require"lxp"
local count = 0
callbacks = {
StartElement = function (parser, name)
io.write("+ ", string.rep(" ", count), name, "\n")
count = count + 1
end,
EndElement = function (parser, name)
count = count - 1
io.write("- ", string.rep(" ", count), name, "\n")
end
}
p = lxp.new(callbacks)
for l in io.lines() do -- iterate lines
p:parse(l) -- parses the line
p:parse("\n") -- parses the end of line
end
p:parse() -- finishes the document
p:close() -- closes the parser
For a test string like
<elem1>
text
<elem2/>
more text
</elem1>
The example would print
+ elem1
+ elem2
- elem2
- elem1
Note that the text parts are not handled since the corresponding callback (CharacterData) has not been defined. Also note that defining this callback after the call to lxp.new would make no difference. But had the callback table been defined as
callbacks = {
StartElement = function (parser, name)
io.write("+ ", string.rep(" ", count), name, "\n")
count = count + 1
end,
EndElement = function (parser, name)
count = count - 1
io.write("- ", string.rep(" ", count), name, "\n")
end,
CharacterData = function (parser, string)
io.write("* ", string.rep(" ", count), string, "\n")
end
}
The results would have been
+ elem1
* text
+ elem2
- elem2
* more text
- elem1
Another example would be the use of false as a placeholder for the callback. Suppose that we would like to print only the text associated with elem2 elements and that the XML sample is
<elem1>
text
<elem2>
inside text
</elem2>
more text
</elem1>
We could define the new callback table as
callbacks = {
StartElement = function (parser, name)
if name == "elem2" then
-- redefines CharacterData behaviour
callbacks.CharacterData = function (parser, string)
io.write(string, "\n")
end
end
end,
EndElement = function (parser, name)
if name == "elem2" then
callbacks.CharacterData = false -- restores placeholder
end
end,
CharacterData = false -- placeholder
}
The results would have been
inside text
Note that this example assumes no other elements are present inside elem2 tags.