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</pre></div><p>This is a basic main() that shows how to create a default settings object tree, save it and load it again:<p><div class="fragment"><pre class="fragment">int main(void){ AppSettings settings; settings.save("appsettings2.xml"); settings.load("appsettings2.xml"); return 0;}</pre></div><p>The following main() shows creation, modification, saving and then loading of a settings structure:<p><div class="fragment"><pre class="fragment">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;}</pre></div><p>When the save() and load() are completed (see below), running this main() displays on the console:<p><div class="fragment"><pre class="fragment">HitchHikerApp: Don't PanicHitchHikerApp: Show window 'BookFrame' at 15,25 (300 x 100)HitchHikerApp: Thanks for all the fish</pre></div><p><h2>Encode C++ state as XML </h2><p>There are lots of different ways to approach saving this to a file. Here's one:<p><div class="fragment"><pre class="fragment">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); }</pre></div><p>Running this with the modified main produces this file:<p><div class="fragment"><pre class="fragment"><?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></pre></div><p><h2>Decoding state from XML </h2><p>As with encoding objects, there are a number of approaches to decoding XML into your own C++ object structure. The following approach uses TiXmlHandles.<p><div class="fragment"><pre class="fragment">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); } }}</pre></div><p><h1>Full listing for dump_to_stdout </h1><p>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.<p><div class="fragment"><pre class="fragment">// 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 endconst 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 STDOUTvoid 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;}</pre></div><p>Run this from the command line or a DOS window, e.g.:<p><div class="fragment"><pre class="fragment">C:\dev\tinyxml> Debug\tinyxml_1.exe example1.xmlexample1.xml:Document+ Declaration+ Element [Hello] (No attributes) + Text: [World]</pre></div><p><em> 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></em> <hr size="1"><address style="align: right;"><small>Generated on Tue Sep 19 19:04:34 2006 for TinyXml by <a href="http://www.doxygen.org/index.html"><img src="doxygen.png" alt="doxygen" align="middle" border="0"></a> 1.4.7 </small></address></body></html>?? 快捷鍵說明
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