tutorial_gettingStarted.txt

/** @page tutorial0 TinyXML Tutorial

<h1> What is this? </h1>

This tutorial has a few tips and suggestions on how to use TinyXML
effectively.

I've also tried to include some C++ tips like how to convert strings to
integers and vice versa. This isn't anything to do with TinyXML itself, but
it may helpful for your project so I've put it in anyway.

If you don't know basic C++ concepts this tutorial won't be useful.
Likewise if you don't know what a DOM is, look elsewhere first.

<h1> Before we start </h1>

Some example XML datasets/files will be used. 

example1.xml:

@verbatim
<?xml version="1.0" ?>
<Hello>World</Hello>
@endverbatim

example2.xml:

@verbatim
<?xml version="1.0" ?>
<poetry>
	<verse>
		Alas
		  Great World
			Alas (again)
	</verse>
</poetry>
@endverbatim

example3.xml:

@verbatim
<?xml version="1.0" ?>
<shapes>
	<circle name="int-based" x="20" y="30" r="50" />
	<point name="float-based" x="3.5" y="52.1" />
</shapes>
@endverbatim

example4.xml

@verbatim
<?xml version="1.0" ?>
<MyApp>
    <!-- Settings for MyApp -->
    <Messages>
        <Welcome>Welcome to MyApp</Welcome>
        <Farewell>Thank you for using MyApp</Farewell>
    </Messages>
    <Windows>
        <Window name="MainFrame" x="5" y="15" w="400" h="250" />
    </Windows>
    <Connection ip="192.168.0.1" timeout="123.456000" />
</MyApp>
@endverbatim

<h1> Getting Started </h1>

<h2> Load XML from a file </h2>

The simplest way to load a file into a TinyXML DOM is:

@verbatim
TiXmlDocument doc( "demo.xml" );
doc.LoadFile();
@endverbatim
	
A more real-world usage is shown below. This will load the file and display
the contents to STDOUT:

@verbatim
// load the named file and dump its structure to STDOUT
void dump_to_stdout(const char* pFilename)
{
	TiXmlDocument doc(pFilename);
	bool loadOkay = doc.LoadFile();
	if (loadOkay)
	{
		printf("\n%s:\n", pFilename);
		dump_to_stdout( &doc ); // defined later in the tutorial
	}
	else
	{
		printf("Failed to load file \"%s\"\n", pFilename);
	}
}
@endverbatim

A simple demonstration of this function is to use a main like this:

@verbatim
int main(void)
{
	dump_to_stdout("example1.xml");
	return 0;
}
@endverbatim

Recall that Example 1 XML is:

@verbatim
<?xml version="1.0" ?>
<Hello>World</Hello>
@endverbatim

Running the program with this XML will display this in the console/DOS window:

@verbatim
DOCUMENT
+ DECLARATION
+ ELEMENT Hello
  + TEXT[World]
@endverbatim


The ``dump_to_stdout`` function is defined later in this tutorial and is
useful if you want to understand recursive traversal of a DOM.

<h2> Building Documents Programatically </h2>


This is how to build Example 1 pragmatically:

@verbatim
void build_simple_doc( )
{
	// Make xml: <?xml ..><Hello>World</Hello>
	TiXmlDocument doc;
	TiXmlDeclaration * decl = new TiXmlDeclaration( "1.0", "", "" );
	TiXmlElement * element = new TiXmlElement( "Hello" );
	TiXmlText * text = new TiXmlText( "World" );
	element->LinkEndChild( text );
	doc.LinkEndChild( decl );
	doc.LinkEndChild( element );
	doc.SaveFile( "madeByHand.xml" );
}
@endverbatim

This can be loaded and displayed on the console with:

@verbatim
dump_to_stdout("madeByHand.xml"); // this func defined later in the tutorial
@endverbatim

and you'll see it is identical to Example 1:

@verbatim
madeByHand.xml:
Document
+ Declaration
+ Element [Hello]
  + Text: [World]
@endverbatim

This code produces exactly the same XML DOM but it shows a different ordering
to node creation and linking:

@verbatim
void write_simple_doc2( )
{
	// same as write_simple_doc1 but add each node
	// as early as possible into the tree.

	TiXmlDocument doc;
	TiXmlDeclaration * decl = new TiXmlDeclaration( "1.0", "", "" );
	doc.LinkEndChild( decl );
	
	TiXmlElement * element = new TiXmlElement( "Hello" );
	doc.LinkEndChild( element );
	
	TiXmlText * text = new TiXmlText( "World" );
	element->LinkEndChild( text );
	
	doc.SaveFile( "madeByHand2.xml" );
}
@endverbatim

Both of these produce the same XML, namely:

@verbatim
<?xml version="1.0" ?>
<Hello>World</Hello>
@endverbatim

Or in structure form:

@verbatim
DOCUMENT
+ DECLARATION
+ ELEMENT Hello
  + TEXT[World]
@endverbatim


<h2> Attributes </h2>

Given an existing node, settings attributes is easy:

@verbatim
window = new TiXmlElement( "Demo" );  
window->SetAttribute("name", "Circle");
window->SetAttribute("x", 5);
window->SetAttribute("y", 15);
window->SetDoubleAttribute("radius", 3.14159);
@endverbatim

You can it also work with the TiXmlAttribute objects if you want.

The following code shows one way (not the only way) to get all attributes of an 
element, print the name and string value, and if the value can be converted
to an integer or double, print that value too:

@verbatim
// print all attributes of pElement.
// returns the number of attributes printed
int dump_attribs_to_stdout(TiXmlElement* pElement, unsigned int indent)
{
	if ( !pElement ) return 0;

	TiXmlAttribute* pAttrib=pElement->FirstAttribute();
	int i=0;
	int ival;
	double dval;
	const char* pIndent=getIndent(indent);
	printf("\n");
	while (pAttrib)
	{
		printf( "%s%s: value=[%s]", pIndent, pAttrib->Name(), pAttrib->Value());

		if (pAttrib->QueryIntValue(&ival)==TIXML_SUCCESS)    printf( " int=%d", ival);
		if (pAttrib->QueryDoubleValue(&dval)==TIXML_SUCCESS) printf( " d=%1.1f", dval);
		printf( "\n" );
		i++;
		pAttrib=pAttrib->Next();
	}
	return i;
}
@endverbatim

<h2> Writing a document to a file </h2>

Writing a pre-built DOM to a file is trivial:

@verbatim
doc.SaveFile( saveFilename );  
@endverbatim

Recall, for example, example 4:

@verbatim
<?xml version="1.0" ?>
<MyApp>
    <!-- Settings for MyApp -->
    <Messages>
        <Welcome>Welcome to MyApp</Welcome>
        <Farewell>Thank you for using MyApp</Farewell>
    </Messages>
    <Windows>
        <Window name="MainFrame" x="5" y="15" w="400" h="250" />
    </Windows>
    <Connection ip="192.168.0.1" timeout="123.456000" />
</MyApp>
@endverbatim

The following function builds this DOM and writes the file "appsettings.xml":

@verbatim
void write_app_settings_doc( )  
{  
	TiXmlDocument doc;  
	TiXmlElement* msg;
 	TiXmlDeclaration* decl = new TiXmlDeclaration( "1.0", "", "" );  
	doc.LinkEndChild( decl );  
 
	TiXmlElement * root = new TiXmlElement( "MyApp" );  
	doc.LinkEndChild( root );  

	TiXmlComment * comment = new TiXmlComment();
	comment->SetValue(" Settings for MyApp " );  
	root->LinkEndChild( comment );  
 
	TiXmlElement * msgs = new TiXmlElement( "Messages" );  
	root->LinkEndChild( msgs );  
 
	msg = new TiXmlElement( "Welcome" );  
	msg->LinkEndChild( new TiXmlText( "Welcome to MyApp" ));  
	msgs->LinkEndChild( msg );  
 
	msg = new TiXmlElement( "Farewell" );  
	msg->LinkEndChild( new TiXmlText( "Thank you for using MyApp" ));  
	msgs->LinkEndChild( msg );  
 
	TiXmlElement * windows = new TiXmlElement( "Windows" );  
	root->LinkEndChild( windows );  

	TiXmlElement * window;
	window = new TiXmlElement( "Window" );  
	windows->LinkEndChild( window );  
	window->SetAttribute("name", "MainFrame");
	window->SetAttribute("x", 5);
	window->SetAttribute("y", 15);
	window->SetAttribute("w", 400);
	window->SetAttribute("h", 250);

	TiXmlElement * cxn = new TiXmlElement( "Connection" );  
	root->LinkEndChild( cxn );  
	cxn->SetAttribute("ip", "192.168.0.1");
	cxn->SetDoubleAttribute("timeout", 123.456); // floating point attrib
	
	dump_to_stdout( &doc );
	doc.SaveFile( "appsettings.xml" );  
} 
@endverbatim

The dump_to_stdout function will show this structure:

@verbatim
Document
+ Declaration
+ Element [MyApp]
 (No attributes)
  + Comment: [ Settings for MyApp ]
  + Element [Messages]
 (No attributes)
    + Element [Welcome]
 (No attributes)
      + Text: [Welcome to MyApp]
    + Element [Farewell]
 (No attributes)
      + Text: [Thank you for using MyApp]
  + Element [Windows]
 (No attributes)
    + Element [Window]
      + name: value=[MainFrame]
      + x: value=[5] int=5 d=5.0
      + y: value=[15] int=15 d=15.0
      + w: value=[400] int=400 d=400.0
      + h: value=[250] int=250 d=250.0
      5 attributes
  + Element [Connection]
    + ip: value=[192.168.0.1] int=192 d=192.2
    + timeout: value=[123.456000] int=123 d=123.5
    2 attributes
@endverbatim


I was surprised that TinyXml, by default, writes the XML in what other
APIs call a "pretty" format - it modifies the whitespace of text of elements 
that contain other nodes so that writing the tree includes an indication of 
nesting level.

I haven't looked yet to see if there is a way to turn off indenting when 
writing a file - its bound to be easy. 

[Lee: It's easy in STL mode, just use cout << myDoc. Non-STL mode is 
always in "pretty" format. Adding a switch would be a nice feature and
has been requested.]


<h1> XML to/from C++ objects </h1>

<h2> Intro </h2>

This example assumes you're loading and saving your app settings in an 
XML file, e.g. something like example4.xml.

There are a number of ways to do this. For example, look into the TinyBind
project at http://sourceforge.net/projects/tinybind

This section shows a plain-old approach to loading and saving a basic object
structure using XML.

<h2> Set up your object classes </h2>

Start off with some basic classes like these:

@verbatim
#include <string>
#include <map>
using namespace std;

typedef std::map<std::string,std::string> MessageMap;

// a basic window abstraction - demo purposes only
class WindowSettings
{
public:
	int x,y,w,h;
	string name;

	WindowSettings()
		: x(0), y(0), w(100), h(100), name("Untitled")
	{
	}

	WindowSettings(int x, int y, int w, int h, const string& name)
	{
		this->x=x;
		this->y=y;
		this->w=w;
		this->h=h;
		this->name=name;
	}
};

class ConnectionSettings
{
public:
	string ip;
	double timeout;
};

class AppSettings
{
public:
	string m_name;
	MessageMap m_messages;
	list<WindowSettings> m_windows;
	ConnectionSettings m_connection;

	AppSettings() {}

	void save(const char* pFilename);
	void load(const char* pFilename);
	
	// just to show how to do it
	void setDemoValues()
	{
		m_name="MyApp";
		m_messages.clear();
		m_messages["Welcome"]="Welcome to "+m_name;
		m_messages["Farewell"]="Thank you for using "+m_name;
		m_windows.clear();
		m_windows.push_back(WindowSettings(15,15,400,250,"Main"));
		m_connection.ip="Unknown";
		m_connection.timeout=123.456;
	}
};
@endverbatim

This is a basic main() that shows how to create a default settings object tree,
save it and load it again:

@verbatim
int main(void)
{
	AppSettings settings;
	
	settings.save("appsettings2.xml");
	settings.load("appsettings2.xml");
	return 0;
}
@endverbatim

The following main() shows creation, modification, saving and then loading of a
settings structure:

@verbatim
int main(void)
{
	// block: customise and save settings
	{
		AppSettings settings;
		settings.m_name="HitchHikerApp";
		settings.m_messages["Welcome"]="Don't Panic";
		settings.m_messages["Farewell"]="Thanks for all the fish";
		settings.m_windows.push_back(WindowSettings(15,25,300,250,"BookFrame"));
		settings.m_connection.ip="192.168.0.77";
		settings.m_connection.timeout=42.0;

		settings.save("appsettings2.xml");
	}
	
	// block: load settings
	{
		AppSettings settings;
		settings.load("appsettings2.xml");
		printf("%s: %s\n", settings.m_name.c_str(), 
			settings.m_messages["Welcome"].c_str());
		WindowSettings & w=settings.m_windows.front();
		printf("%s: Show window '%s' at %d,%d (%d x %d)\n", 
			settings.m_name.c_str(), w.name.c_str(), w.x, w.y, w.w, w.h);
		printf("%s: %s\n", settings.m_name.c_str(), settings.m_messages["Farewell"].c_str());
	}
	return 0;
}
@endverbatim

When the save() and load() are completed (see below), running this main() 
displays on the console:

@verbatim
HitchHikerApp: Don't Panic
HitchHikerApp: Show window 'BookFrame' at 15,25 (300 x 100)
HitchHikerApp: Thanks for all the fish
@endverbatim

<h2> Encode C++ state as XML </h2>

There are lots of different ways to approach saving this to a file.
Here's one:

@verbatim
void AppSettings::save(const char* pFilename)
{
	TiXmlDocument doc;  
	TiXmlElement* msg;
	TiXmlComment * comment;
	string s;
 	TiXmlDeclaration* decl = new TiXmlDeclaration( "1.0", "", "" );  
	doc.LinkEndChild( decl ); 
 
	TiXmlElement * root = new TiXmlElement(m_name.c_str());  
	doc.LinkEndChild( root );  

	comment = new TiXmlComment();
	s=" Settings for "+m_name+" ";
	comment->SetValue(s.c_str());  
	root->LinkEndChild( comment );  

	// block: messages
	{
		MessageMap::iterator iter;

		TiXmlElement * msgs = new TiXmlElement( "Messages" );  
		root->LinkEndChild( msgs );  
 
		for (iter=m_messages.begin(); iter != m_messages.end(); iter++)
		{
			const string & key=(*iter).first;
			const string & value=(*iter).second;
			msg = new TiXmlElement(key.c_str());  
			msg->LinkEndChild( new TiXmlText(value.c_str()));  
			msgs->LinkEndChild( msg );  
		}
	}

	// block: windows
	{
		TiXmlElement * windowsNode = new TiXmlElement( "Windows" );  
		root->LinkEndChild( windowsNode );  

		list<WindowSettings>::iterator iter;

		for (iter=m_windows.begin(); iter != m_windows.end(); iter++)
		{
			const WindowSettings& w=*iter;

			TiXmlElement * window;
			window = new TiXmlElement( "Window" );  
			windowsNode->LinkEndChild( window );  
			window->SetAttribute("name", w.name.c_str());
			window->SetAttribute("x", w.x);
			window->SetAttribute("y", w.y);
			window->SetAttribute("w", w.w);
			window->SetAttribute("h", w.h);
		}
	}

	// block: connection
	{
		TiXmlElement * cxn = new TiXmlElement( "Connection" );  
		root->LinkEndChild( cxn );  
		cxn->SetAttribute("ip", m_connection.ip.c_str());
		cxn->SetDoubleAttribute("timeout", m_connection.timeout); 
	}

	doc.SaveFile(pFilename);  
}
@endverbatim

Running this with the modified main produces this file:

@verbatim
<?xml version="1.0" ?>
<HitchHikerApp>
    <!-- Settings for HitchHikerApp -->
    <Messages>
        <Farewell>Thanks for all the fish</Farewell>
        <Welcome>Don&apos;t Panic</Welcome>
    </Messages>
    <Windows>
        <Window name="BookFrame" x="15" y="25" w="300" h="250" />
    </Windows>
    <Connection ip="192.168.0.77" timeout="42.000000" />
</HitchHikerApp>
@endverbatim


<h2> Decoding state from XML </h2>

As with encoding objects, there are a number of approaches to decoding XML
into your own C++ object structure. The following approach uses TiXmlHandles.

@verbatim
void AppSettings::load(const char* pFilename)
{
	TiXmlDocument doc(pFilename);
	if (!doc.LoadFile()) return;

	TiXmlHandle hDoc(&doc);
	TiXmlElement* pElem;
	TiXmlHandle hRoot(0);

	// block: name
	{
		pElem=hDoc.FirstChildElement().Element();
		// should always have a valid root but handle gracefully if it does
		if (!pElem) return;
		m_name=pElem->Value();

		// save this for later
		hRoot=TiXmlHandle(pElem);
	}

	// block: string table
	{
		m_messages.clear(); // trash existing table

		pElem=hRoot.FirstChild( "Messages" ).FirstChild().Element();
		for( pElem; pElem; pElem=pElem->NextSiblingElement())
		{
			const char *pKey=pElem->Value();
			const char *pText=pElem->GetText();
			if (pKey && pText) 
			{
				m_messages[pKey]=pText;
			}
		}
	}

	// block: windows
	{
		m_windows.clear(); // trash existing list

		TiXmlElement* pWindowNode=hRoot.FirstChild( "Windows" ).FirstChild().Element();
		for( pWindowNode; pWindowNode; pWindowNode=pWindowNode->NextSiblingElement())
		{
			WindowSettings w;
			const char *pName=pWindowNode->Attribute("name");
			if (pName) w.name=pName;
			
			pWindowNode->QueryIntAttribute("x", &w.x); // If this fails, original value is left as-is
			pWindowNode->QueryIntAttribute("y", &w.y);
			pWindowNode->QueryIntAttribute("w", &w.w);
			pWindowNode->QueryIntAttribute("hh", &w.h);

			m_windows.push_back(w);
		}
	}

	// block: connection
	{
		pElem=hRoot.FirstChild("Connection").Element();
		if (pElem)
		{
			m_connection.ip=pElem->Attribute("ip");
			pElem->QueryDoubleAttribute("timeout",&m_connection.timeout);
		}
	}
}
@endverbatim

<h1> Full listing for dump_to_stdout </h1>

Below is a copy-and-paste demo program for loading arbitrary XML files and
dumping the structure to STDOUT using the recursive traversal listed above.

@verbatim
// tutorial demo program
#include "stdafx.h"
#include "tinyxml.h"

// ----------------------------------------------------------------------
// STDOUT dump and indenting utility functions
// ----------------------------------------------------------------------
const unsigned int NUM_INDENTS_PER_SPACE=2;

const char * getIndent( unsigned int numIndents )
{
	static const char * pINDENT="                                      + ";
	static const unsigned int LENGTH=strlen( pINDENT );
	unsigned int n=numIndents*NUM_INDENTS_PER_SPACE;
	if ( n > LENGTH ) n = LENGTH;

	return &pINDENT[ LENGTH-n ];
}

// same as getIndent but no "+" at the end
const char * getIndentAlt( unsigned int numIndents )
{
	static const char * pINDENT="                                        ";
	static const unsigned int LENGTH=strlen( pINDENT );
	unsigned int n=numIndents*NUM_INDENTS_PER_SPACE;
	if ( n > LENGTH ) n = LENGTH;

	return &pINDENT[ LENGTH-n ];
}

int dump_attribs_to_stdout(TiXmlElement* pElement, unsigned int indent)
{
	if ( !pElement ) return 0;

	TiXmlAttribute* pAttrib=pElement->FirstAttribute();
	int i=0;
	int ival;
	double dval;
	const char* pIndent=getIndent(indent);
	printf("\n");
	while (pAttrib)
	{
		printf( "%s%s: value=[%s]", pIndent, pAttrib->Name(), pAttrib->Value());

		if (pAttrib->QueryIntValue(&ival)==TIXML_SUCCESS)    printf( " int=%d", ival);
		if (pAttrib->QueryDoubleValue(&dval)==TIXML_SUCCESS) printf( " d=%1.1f", dval);
		printf( "\n" );
		i++;
		pAttrib=pAttrib->Next();
	}
	return i;	
}

void dump_to_stdout( TiXmlNode* pParent, unsigned int indent = 0 )
{
	if ( !pParent ) return;

	TiXmlNode* pChild;
	TiXmlText* pText;
	int t = pParent->Type();
	printf( "%s", getIndent(indent));
	int num;

	switch ( t )
	{
	case TiXmlNode::DOCUMENT:
		printf( "Document" );
		break;

	case TiXmlNode::ELEMENT:
		printf( "Element [%s]", pParent->Value() );
		num=dump_attribs_to_stdout(pParent->ToElement(), indent+1);
		switch(num)
		{
			case 0:  printf( " (No attributes)"); break;
			case 1:  printf( "%s1 attribute", getIndentAlt(indent)); break;
			default: printf( "%s%d attributes", getIndentAlt(indent), num); break;
		}
		break;

	case TiXmlNode::COMMENT:
		printf( "Comment: [%s]", pParent->Value());
		break;

	case TiXmlNode::UNKNOWN:
		printf( "Unknown" );
		break;

	case TiXmlNode::TEXT:
		pText = pParent->ToText();
		printf( "Text: [%s]", pText->Value() );
		break;

	case TiXmlNode::DECLARATION:
		printf( "Declaration" );
		break;
	default:
		break;
	}
	printf( "\n" );
	for ( pChild = pParent->FirstChild(); pChild != 0; pChild = pChild->NextSibling()) 
	{
		dump_to_stdout( pChild, indent+1 );
	}
}

// load the named file and dump its structure to STDOUT
void dump_to_stdout(const char* pFilename)
{
	TiXmlDocument doc(pFilename);
	bool loadOkay = doc.LoadFile();
	if (loadOkay)
	{
		printf("\n%s:\n", pFilename);
		dump_to_stdout( &doc ); // defined later in the tutorial
	}
	else
	{
		printf("Failed to load file \"%s\"\n", pFilename);
	}
}

// ----------------------------------------------------------------------
// main() for printing files named on the command line
// ----------------------------------------------------------------------
int main(int argc, char* argv[])
{
	for (int i=1; i<argc; i++)
	{
		dump_to_stdout(argv[i]);
	}
	return 0;
}
@endverbatim

Run this from the command line or a DOS window, e.g.:

@verbatim
C:\dev\tinyxml> Debug\tinyxml_1.exe example1.xml

example1.xml:
Document
+ Declaration
+ Element [Hello]
 (No attributes)
  + Text: [World]
@endverbatim

<i> Authors and Changes
<ul>
<li> Written by Ellers, April, May, June 2005 </li>
<li> Minor edits and integration into doc system, Lee Thomason September 2005 </li>
<li> Updated by Ellers, October 2005 </li>
</ul>
</i>

*/