I read the tutorial at https://coronalabs.com/blog/2011/07/29/how-to-use-xml-files-in-corona/ and it goes over reading an XML file from an external module. what I am trying to do is access some XML from a website and then parse it for some required information.
I should be able to use that XML parser, but I’m not sure how to get the XML from a website rather than a local file. I would appreciate any pointers as to how to do this.
You use network.request() to get the data. It will end up in a Lua string that you can then pass to the XML parser to turn it into a Lua table.
Rob
So my network request will be:
local returnstring = network.request(url)
Not sure of the syntax for calling the parser for a variable instead of a file. From the tutorial, I see:
local inbox = xml:loadFile( “sample.xml” )
It won’t be xml:loadFile, but xml:parseXMLText(returnstring)?
network.request does’t return data that way. It’s an asyncromous function in that it returns to your program right away before the request completes. You have to provide a call back function (listener) that will be evoked when the request is complete. Please see:
Then something like this?
local function networkListener( event )
if ( event.isError ) then
print ( “Network error!”)
else
local xmltable=xml:parseXMLText(event.response)
end
end
network.request( <url goes here>, “GET”, networkListener )
That looks about right…
Rob
My listener function looks like this:
[lua]
local function networkListener( event )
if ( event.isError ) then
print ( “Network error!”)
else
local xmltable=xml:ParseXmlText(event.response)
--print (event.response)
print (xmltable.child[1].child[1].child[1].value)
--print (xmltable.child[1].child[1].child[2].value)
end
end[/lua]
and the XML string being parsed is this:
This XML file does not appear to have any style information associated with it. The document tree is shown below.
<query xmlns:yahoo=“http://www.yahooapis.com/v1/base.rng” yahoo:count=“2” yahoo:created=“2014-02-07T02:07:33Z” yahoo:lang=“en-US”>
<results>
<quote>
<LastTradePriceOnly>107.45</LastTradePriceOnly>
</quote>
<quote>
<LastTradePriceOnly>97.82</LastTradePriceOnly>
</quote>
</results>
</query>
<!-- total: 92 -->
<!-- engine7.yql.bf1.yahoo.com -->
When I run my code, it seems to work erratically. Sometimes
print (xmltable.child[1].child[1].child[1].value)
gives me the answer I am looking for. Other times it blows up with an error in the terminal
Runtime error
…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: attempt to index field ‘?’ (a nil value)
stack traceback:
[C]: ?
…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: in function <…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:112>
Runtime error: …ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: attempt to index field ‘?’ (a nil value)
stack traceback:
[C]: ?
…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: in function <…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:112>
Also, when I try and print (xmltable.child[1].child[1].child[2].value) it always gives the run time error.
Any ideas as to why this is happening?
Just solved my own issue. I was looking for the wrong table value. instead of (xmltable.child[1].child[1].child[2].value) the second number is (xmltable.child[1].child[2].child[1].value).
You use network.request() to get the data. It will end up in a Lua string that you can then pass to the XML parser to turn it into a Lua table.
Rob
So my network request will be:
local returnstring = network.request(url)
Not sure of the syntax for calling the parser for a variable instead of a file. From the tutorial, I see:
local inbox = xml:loadFile( “sample.xml” )
It won’t be xml:loadFile, but xml:parseXMLText(returnstring)?
network.request does’t return data that way. It’s an asyncromous function in that it returns to your program right away before the request completes. You have to provide a call back function (listener) that will be evoked when the request is complete. Please see:
Then something like this?
local function networkListener( event )
if ( event.isError ) then
print ( “Network error!”)
else
local xmltable=xml:parseXMLText(event.response)
end
end
network.request( <url goes here>, “GET”, networkListener )
That looks about right…
Rob
My listener function looks like this:
[lua]
local function networkListener( event )
if ( event.isError ) then
print ( “Network error!”)
else
local xmltable=xml:ParseXmlText(event.response)
--print (event.response)
print (xmltable.child[1].child[1].child[1].value)
--print (xmltable.child[1].child[1].child[2].value)
end
end[/lua]
and the XML string being parsed is this:
This XML file does not appear to have any style information associated with it. The document tree is shown below.
<query xmlns:yahoo=“http://www.yahooapis.com/v1/base.rng” yahoo:count=“2” yahoo:created=“2014-02-07T02:07:33Z” yahoo:lang=“en-US”>
<results>
<quote>
<LastTradePriceOnly>107.45</LastTradePriceOnly>
</quote>
<quote>
<LastTradePriceOnly>97.82</LastTradePriceOnly>
</quote>
</results>
</query>
<!-- total: 92 -->
<!-- engine7.yql.bf1.yahoo.com -->
When I run my code, it seems to work erratically. Sometimes
print (xmltable.child[1].child[1].child[1].value)
gives me the answer I am looking for. Other times it blows up with an error in the terminal
Runtime error
…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: attempt to index field ‘?’ (a nil value)
stack traceback:
[C]: ?
…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: in function <…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:112>
Runtime error: …ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: attempt to index field ‘?’ (a nil value)
stack traceback:
[C]: ?
…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:120: in function <…ers/seandzafovic/Desktop/Volume App 2/data_entry.lua:112>
Also, when I try and print (xmltable.child[1].child[1].child[2].value) it always gives the run time error.
Any ideas as to why this is happening?
Just solved my own issue. I was looking for the wrong table value. instead of (xmltable.child[1].child[1].child[2].value) the second number is (xmltable.child[1].child[2].child[1].value).