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Diffstat (limited to 'libs/property_tree/doc/tutorial.qbk')
| -rw-r--r-- | libs/property_tree/doc/tutorial.qbk | 91 |
1 files changed, 15 insertions, 76 deletions
diff --git a/libs/property_tree/doc/tutorial.qbk b/libs/property_tree/doc/tutorial.qbk index 4d374c368..9ef3a922d 100644 --- a/libs/property_tree/doc/tutorial.qbk +++ b/libs/property_tree/doc/tutorial.qbk @@ -1,14 +1,16 @@ [/ / Copyright (c) 2008 Marcin Kalicinski (kalita <at> poczta dot onet dot pl) - / Copyright (c) 2009 Sebastian Redl (sebastian dot redl <at> getdesigned dot at) + / Copyright (c) 2009, 2013 Sebastian Redl (sebastian dot redl <at> getdesigned dot at) / / Distributed under the Boost Software License, Version 1.0. (See accompanying / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) /] [section:tutorial Five Minute Tutorial] +[import ../examples/debug_settings.cpp] + This tutorial uses XML. Note that the library is not specifically bound to XML, and any other supported format (such as INI or JSON) could be used instead. -XML was chosen because the author thinks that wide range of people is familiar +XML was chosen because the author thinks that a wide range of people is familiar with it. Suppose we are writing a logging system for some application, and need to read @@ -28,89 +30,26 @@ configuration looks like this: ] It contains the log filename, a list of modules where logging is enabled, and -the debug level value. To store the logging configuration in the program we -created a debug_settings structure: - - struct debug_settings - { - std::string m_file; // log filename - int m_level; // debug level - std::set<string> m_modules; // modules where logging is enabled - void load(const std::string &filename); - void save(const std::string &filename); - }; - -All that needs to be done now is to write implementations of load() and save() -member functions. Let's first deal with load(). It contains just 7 lines of -code, although it does all the necessary things, including error reporting: +the debug level value. - #include <boost/property_tree/ptree.hpp> - #include <boost/property_tree/xml_parser.hpp> +First we need some includes: - // Loads debug_settings structure from the specified XML file - void debug_settings::load(const std::string &filename) - { - // Create an empty property tree object - using boost::property_tree::__ptree__; - __ptree__ pt; +[debug_settings_includes] - // Load the XML file into the property tree. If reading fails - // (cannot open file, parse error), an exception is thrown. - __read_xml__(filename, pt); +To store the logging configuration in the program we create a debug_settings +structure: - // Get the filename and store it in the m_file variable. - // Note that we construct the path to the value by separating - // the individual keys with dots. If dots appear in the keys, - // a path type with a different separator can be used. - // If the debug.filename key is not found, an exception is thrown. - m_file = pt.__ptree_get__<std::string>("debug.filename"); +[debug_settings_data] - // Get the debug level and store it in the m_level variable. - // This is another version of the get method: if the value is - // not found, the default value (specified by the second - // parameter) is returned instead. The type of the value - // extracted is determined by the type of the second parameter, - // so we can simply write get(...) instead of get<int>(...). - m_level = pt.__ptree_get__("debug.level", 0); +All that needs to be done now is to write implementations of load() and save() +member functions. Let's first deal with load(). It contains just 7 lines of +code, although it does all the necessary things, including error reporting: - // Iterate over the debug.modules section and store all found - // modules in the m_modules set. The get_child() function - // returns a reference to the child at the specified path; if - // there is no such child, it throws. Property tree iterators - // are models of BidirectionalIterator. - BOOST_FOREACH(__ptree__::__ptree_value_type__ &v, - pt.__ptree_get_child__("debug.modules")) - m_modules.__ptree_insert__(v.second.data()); - } +[debug_settings_load] Now the save() function. It is also 7 lines of code: - // Saves the debug_settings structure to the specified XML file - void debug_settings::save(const std::string &filename) - { - // Create an empty property tree object - using boost::property_tree::__ptree__; - __ptree__ pt; - - // Put log filename in property tree - pt.__ptree_put__("debug.filename", m_file); - - // Put debug level in property tree - pt.__ptree_put__("debug.level", m_level); - - // Iterate over the modules in the set and put them in the - // property tree. Note that the put function places the new - // key at the end of the list of keys. This is fine most of - // the time. If you want to place an item at some other place - // (i.e. at the front or somewhere in the middle), this can - // be achieved using a combination of the insert and put_own - // functions. - BOOST_FOREACH(const std::string &name, m_modules) - pt.__ptree_add__("debug.modules.module", name); - - // Write the property tree to the XML file. - __write_xml__(filename, pt); - } +[debug_settings_save] The full program [@boost:/libs/property_tree/examples/debug_settings.cpp debug_settings.cpp] is included in the examples directory. |