I am using boost for the first time within an old code base that we have
iptree children = pt.get_child(fieldName);
for (const auto& kv : children) {
boost::property_tree::iptree subtree = (boost::property_tree::iptree) kv.second ;
//Recursive call
}
My problem is sometimes the fieldName doesn`t exist in the XML file and I have an exception
I tried :
boost::property_tree::iptree::assoc_iterator it = pt.find(fieldName);
but I dont know how to use the it I can`t use: if (it != null)
Any help please will be appreciated
I am using VS 2012
If it`s very complicated is there any other way to read a XML with nested nodes? I am working on that since 3 days
This is an Example of the XML
<?xml version="1.0" encoding="utf-8"?>
<nodeA xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<nodeA.1>This is the Adresse</nodeA.1>
<nodeA.2>
<node1>
<node1.1>
<node1.1.1>Female</node1.1.1>
<node1.1.2>23</node1.1.2>
<node1.1.3>Engineer</node1.1.3>
</node1.1>
<node1.2>
<node1.2.1>Female</node1.2.1>
<node1.2.2>35</node1.2.2>
<node1.2.3>Doctors</node1.2.3>
</node1.2>
</node1>
</nodeA.2>
<nodeA.3>Car 1</nodeA.3>
</nodeA>
Use pt.get_child_optional(...) to prevent an exception. pt.find(...) returns an iterator which compares true to pt.not_found() on failure.
EDIT: How to use boost::optional<--->
boost::optional< iptree & > chl = pt.get_child_optional(fieldname);
if(chl) {
for( auto a : *chl )
std::cerr << ":" << a.first << ":" << std::endl;
}
Related
I'm writing a class derived from wxStyledTextCtrl and I want it to prettify given XML without adding anything other than whitespaces. I cannot find simple working solution. I can only use wxStyledTextCtrl, wxXmlDocument and libxml2.
The result I'm aiming for is that after calling SetText with wxString containing following text
<!-- comment1 --> <!-- comment2 --> <node><emptynode/> <othernode>value</othernode></node>
the control should show
<!-- comment1 -->
<!-- comment2 -->
<node>
<emptynode/>
<othernode>value</othernode>
</node>
using libxml2 I managed to almost achieve this, but it also prints XML declaration (eg. <?xml version="1.0" encoding="UTF-8"?>) and I don't want this.
inb4, I'm looking for simple and clean solution - i don't want to manually remove first line of formatted XML
Is there any simple solution to this using given tools? I feel like I'm missing something.
Is there a simple solution? No. But if you want to write you're own pretty print function, you basically need to make a depth first iteration over the xml document tree, printing it as you go. There's a slight complication in that you also need some way of knowing when to close a tag.
Here's an incomplete example of one way to do this using only wxWidgets xml classes. Currently, it doesn't handle attributes, self closing elements (such as '' in your sample text), or any other special element types. A complete pretty printer would need to add those things.
#include <stack>
#include <set>
#include <wx/xml/xml.h>
#include <wx/sstream.h>
wxString PrettyPrint(const wxString& in)
{
wxStringInputStream string_stream(in);
wxXmlDocument doc(string_stream);
wxString pretty_print;
if (doc.IsOk())
{
std::stack<wxXmlNode*> nodes_in_progress;
std::set<wxXmlNode*> visited_nodes;
nodes_in_progress.push(doc.GetDocumentNode());
while (!nodes_in_progress.empty())
{
wxXmlNode* cur_node = nodes_in_progress.top();
nodes_in_progress.pop();
int depth = cur_node->GetDepth();
for (int i=1;i<depth;++i)
{
pretty_print << "\t";
}
if (visited_nodes.find(cur_node)!=visited_nodes.end())
{
pretty_print << "</" << cur_node->GetName() << ">\n";
}
else if ( !cur_node->GetNodeContent().IsEmpty() )
{
//If the node has content, just print it now
pretty_print << "<" << cur_node->GetName() << ">";
pretty_print << cur_node->GetNodeContent() ;
pretty_print << "</" << cur_node->GetName() << ">\n";
}
else if (cur_node==doc.GetDocumentNode())
{
std::stack<wxXmlNode *> nodes_to_add;
wxXmlNode *child = cur_node->GetChildren();
while (child)
{
nodes_to_add.push(child);
child = child->GetNext();
}
while (!nodes_to_add.empty())
{
nodes_in_progress.push(nodes_to_add.top());
nodes_to_add.pop();
}
}
else if (cur_node->GetType()==wxXML_COMMENT_NODE)
{
pretty_print << "<!-- " << cur_node->GetContent() << " -->\n";
}
//insert checks for other types of nodes with special
//printing requirements here
else
{
//otherwise, mark the node as visited and then put it back
visited_nodes.insert(cur_node);
nodes_in_progress.push(cur_node);
//If we push the children in order, they'll be popped
//in reverse order.
std::stack<wxXmlNode *> nodes_to_add;
wxXmlNode *child = cur_node->GetChildren();
while (child)
{
nodes_to_add.push(child);
child = child->GetNext();
}
while (!nodes_to_add.empty())
{
nodes_in_progress.push(nodes_to_add.top());
nodes_to_add.pop();
}
pretty_print <<"<" << cur_node->GetName() << ">\n";
}
}
}
return pretty_print;
}
I can successfully use Xerces XPath feature to query for information from an XML with the following XML and C++ code.
XML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<root>
<ApplicationSettings>
hello universe
</ApplicationSettings>
</root>
C++
int main()
{
XMLPlatformUtils::Initialize();
// create the DOM parser
XercesDOMParser *parser = new XercesDOMParser;
parser->setValidationScheme(XercesDOMParser::Val_Never);
parser->parse("fake_cmf.xml");
// get the DOM representation
DOMDocument *doc = parser->getDocument();
// get the root element
DOMElement* root = doc->getDocumentElement();
// evaluate the xpath
DOMXPathResult* result=doc->evaluate(
XMLString::transcode("/root/ApplicationSettings"), // <-- HERE IS THE XPATH
root,
NULL,
DOMXPathResult::ORDERED_NODE_SNAPSHOT_TYPE, //DOMXPathResult::ANY_UNORDERED_NODE_TYPE, //DOMXPathResult::STRING_TYPE,
NULL);
// look into the xpart evaluate result
result->snapshotItem(0);
std::cout<<TranscodeToStr(result->getNodeValue()->getFirstChild()->getNodeValue(),"ascii").str()<<std::endl;;
XMLPlatformUtils::Terminate();
return 0;
}
The problem is that sometimes my XML will only have certain fields. But if I remove the ApplicationSettings entry from the XML it will seg fault. How can I properly handle these optional fields? I know that trying to correct from seg faults is risky business.
The seg fault is occurring in this line
std::cout<<TranscodeToStr(result->getNodeValue()->getFirstChild()->getNodeValue(),"ascii").str()<<std::endl;
specifically in get getFirstChild() call because the result of getNodeValue() is NULL.
This is my quick and dirty solution. It's not really ideal but it works. I would prefer a more sophisticated evaluation and response.
if (result->getNodeValue() == NULL)
{
cout << "There is no result for the provided XPath " << endl;
}
else
{
cout<<TranscodeToStr(result->getNodeValue()->getFirstChild()->getNodeValue(),"ascii").str()<<endl;
}
I am trying to fetch, internet time using a web service, which provides me an xml. Now, I am trying to parse the xml file using pugixml. The XML returned
<?xml version="1.0" encoding="ISO-8859-1" ?>
<timezone xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://www.earthtools.org/timezone.xsd">
<version>1.0</version>
<location>
<latitude>22.5667</latitude>
<longitude>88.3667</longitude>
</location>
<offset>5.5</offset>
<suffix>E*</suffix>
<localtime>20 Jul 2014 14:48:10</localtime>
<isotime>2014-07-20 14:48:10 +0530</isotime>
<utctime>2014-07-20 09:18:10</utctime>
<dst>Unknown</dst>
</timezone>
The way I am trying to parse it.
pugi::xml_document doc;
if (!doc.load_file("time.xml")) return -1;
pugi::xml_node tools = doc.child("timezone").child("localtime");
//[code_traverse_iter
for (pugi::xml_node_iterator it = tools.begin(); it != tools.end(); ++it)
{
std::cout << "Tool:";
for (pugi::xml_attribute_iterator ait = it->attributes_begin(); ait != it->attributes_end(); ++ait)
{
std::cout << " " << ait->name() << "=" << ait->value();
}
std::cout << std::endl;
}
return 0;
I need fetch the value of this node
<localtime>20 Jul 2014 14:48:10</localtime>
Please help me get through this.
P.S: The web-service I am using can be found http://www.earthtools.org/webservices.htm, hope it helps someone.
I know I can do a simple file operation to fetch the data as the xml is not that long, but still I would like to use the parser.
const char* localtime = doc.child("timezone").child("localtime").text().get();
or
const char* localtime = doc.child("timezone").child_value("localtime");
Hi
I want to use XML file as a config file, from which I will read parameters for my application. I came across on PugiXML library, however I have problem with getting values of attributes.
My XML file looks like that
<?xml version="1.0"?>
<settings>
<deltaDistance> </deltaDistance>
<deltaConvergence>0.25 </deltaConvergence>
<deltaMerging>1.0 </deltaMerging>
<m> 2</m>
<multiplicativeFactor>0.7 </multiplicativeFactor>
<rhoGood> 0.7 </rhoGood>
<rhoMin>0.3 </rhoMin>
<rhoSelect>0.6 </rhoSelect>
<stuckProbability>0.2 </stuckProbability>
<zoneOfInfluenceMin>2.25 </zoneOfInfluenceMin>
</settings>
To pare XML file I use this code
void ReadConfig(char* file)
{
pugi::xml_document doc;
if (!doc.load_file(file)) return false;
pugi::xml_node tools = doc.child("settings");
//[code_traverse_iter
for (pugi::xml_node_iterator it = tools.begin(); it != tools.end(); ++it)
{
cout<<it->name() << " " << it->attribute(it->name()).as_double();
}
}
and I also was trying to use this
void ReadConfig(char* file)
{
pugi::xml_document doc;
if (!doc.load_file(file)) return false;
pugi::xml_node tools = doc.child("settings");
//[code_traverse_iter
for (pugi::xml_node_iterator it = tools.begin(); it != tools.end(); ++it)
{
cout<<it->name() << " " << it->value();
}
}
Attributes are loaded corectly , however all values are equals 0. Could somebody tell me what I do wrong ?
I think your problem is that you're expecting the value to be stored in the node itself, but it's really in a CHILD text node. A quick scan of the documentation showed that you might need
it->child_value()
instead of
it->value()
Are you trying to get all the attributes for a given node or do you want to get the attributes by name?
For the first case, you should be able to use this code:
unsigned int numAttributes = node.attributes();
for (unsigned int nAttribute = 0; nAttribute < numAtributes; ++nAttribute)
{
pug::xml_attribute attrib = node.attribute(nAttribute);
if (!attrib.empty())
{
// process here
}
}
For the second case:
LPCTSTR GetAttribute(pug::xml_node & node, LPCTSTR szAttribName)
{
if (szAttribName == NULL)
return NULL;
pug::xml_attribute attrib = node.attribute(szAttribName);
if (attrib.empty())
return NULL; // or empty string
return attrib.value();
}
If you want stock plain text data into the nodes like
<name> My Name</name>
You need to make it like
rootNode.append_child("name").append_child(node_pcdata).set_value("My name");
If you want to store datatypes, you need to set an attribute. I think what you want is to be able to read the value directly right?
When you are writing the node,
rootNode.append_child("version").append_attribute("value").set_value(0.11)
When you want to read it,
rootNode.child("version").attribute("version").as_double()
At least that's my way of doing it!
yester day was my first attempt. I am trying to catch the variable "time" in the following "new.xml" file
<?xml version="1.0" standalone=no>
<main>
<ToDo time="1">
<Item priority="1"> Go to the <bold>Toy store!</bold></Item>
<Item priority="2"> Do bills</Item>
</ToDo>
<ToDo time="2">
<Item priority="1"> Go to the Second<bold>Toy store!</bold></Item>
</ToDo>
</main>
Here is my code
TiXmlDocument doc("new.xml");
TiXmlNode * element=doc.FirstChild("main");
element=element->FirstChild("ToDo");
string temp=static_cast<TiXmlElement *>(element)->Attribute("time");
But I am getting run time errors from the third and fourth lines. Can anybody shed a light on this isssue?
It seems to me that you forgot to load the file. Normally I do something along these lines:
TiXmlDocument doc("document.xml");
bool loadOkay = doc.LoadFile(); // Error checking in case file is missing
if(loadOkay)
{
TiXmlElement *pRoot = doc.RootElement();
TiXmlElement *element = pRoot->FirstChildElement();
while(element)
{
string value = firstChild->Value(); // In your example xml file this gives you ToDo
string attribute = firstChild->Attribute("time"); //Gets you the time variable
element = element->NextSiblingElement();
}
}
else
{
//Error conditions
}
Hope this helps
#include "tinyXml/tinyxml.h"
const char MY_XML[] = "<?xml version='1.0' standalone=no><main> <ToDo time='1'> <Item priority='1'> Go to the <bold>Toy store!</bold></Item> <Item priority='2'> Do bills</Item> </ToDo> <ToDo time='2'> <Item priority='1'> Go to the Second<bold>Toy store!</bold></Item> </ToDo></main>";
void main()
{
TiXmlDocument doc;
TiXmlHandle docHandle(&doc);
const char * const the_xml = MY_XML;
doc.Parse(MY_XML);
TiXmlElement* xElement = NULL;
xElement = docHandle.FirstChild("main").FirstChild("ToDo").ToElement();
int element_time = -1;
while(xElement)
{
if(xElement->QueryIntAttribute("time", (int*)&element_time) != TIXML_SUCCESS)
throw;
xElement = xElement->NextSiblingElement();
}
}
That's how it works. Compiled & tested.
As you can see your tries to make it extra-safe code cost you with an exceotion at your third line (of the question), and without testing I can bet it's a "pointing-to-null" exception.
Just load it my style, as TinyXml's docs say as well: "docHandle.FirstChild("main").FirstChild("ToDo").ToElement();".
Hope it helps you understand, let me know if it's not clear. I accept visa (:
Is it just me or the the pugixml version looks much better?
#include <iostream>
#include "pugixml.hpp"
using namespace std;
using namespace pugi;
int main()
{
xml_document doc;
if (!doc.load_file("new.xml"))
{
cerr << "Could not load xml";
return 1;
}
xml_node element = doc.child("main");
element = element.child("ToDo");
cout << "Time: " << element.attribute("time") << endl;
}
Also new.xml had an error, instead of:
<?xml version="1.0" standalone=no>
should be
<?xml version="1.0" standalone="no"?>
Compilation was just a matter of cl test.cpp pugixml.cpp