Wt  3.3.9
Public Types | Public Member Functions | List of all members
Wt::WMessageResourceBundle Class Reference

Support for localized strings using XML files. More...

#include <Wt/WMessageResourceBundle>

Inheritance diagram for Wt::WMessageResourceBundle:
Inheritance graph
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Public Types

Public Member Functions

 WMessageResourceBundle ()
 Creates a message resource bundle.
 
void use (const std::string &path, bool loadInMemory=true)
 Adds a (series) of message resource files to be used. More...
 
const std::set< std::string > keys (WFlags< Scope > scope) const
 Returns a set of all keys in this bundle. More...
 
virtual void refresh ()
 Rereads the message resources. More...
 
virtual void hibernate ()
 Purges memory resources, if possible. More...
 
virtual bool resolveKey (const std::string &key, std::string &result)
 Resolves a key in the current locale. More...
 
virtual bool resolvePluralKey (const std::string &key, std::string &result,::uint64_t amount)
 Resolves the plural form of a key in the current locale. More...
 
- Public Member Functions inherited from Wt::WLocalizedStrings
virtual ~WLocalizedStrings ()
 Destructor.
 

Additional Inherited Members

- Static Public Member Functions inherited from Wt::WLocalizedStrings
static int evaluatePluralExpression (const std::string &expression,::uint64_t n)
 Utility method to evaluate a plural expression. More...
 

Detailed Description

Support for localized strings using XML files.

The resource bundle manages a number of resource files, which allow the developer to conceptually manage its messages in a number of libraries.

For example, a WApplication may have a generic message library, that is shared with many other libraries, with re-occurring messages (such as 'welcome', 'add to shopping cart', and 'pay'), and a specific message library for specific messages.

Usage example:

XML file "general.xml":

 <?xml version="1.0" encoding="UTF-8"?>
 <messages>

   <message id='welcome-text'>
     Welcome dear visiter, {1} of the WFooBar magic website !
   </message>

   <message id='company-policy'>
     The company policy is to <b>please our share-holders</b>.
   </message>

 </messages>

The encodings supported are ASCII, UTF-8 (recommended) or UTF-16.

Use this resource bundle in your program:

// load the message resource bundle
app->messageResourceBundle().use("general");
// resolve a string using the resource bundle
Wt::WText *welcome = new Wt::WText(tr("welcome-visitor").arg("Bart"));

To refer the two messages defined in this resource file, use WString::tr("welcome-text").arg(userName) or WWidget::tr("company-policy").

Plural forms

The XML format supports plural noun forms, and allows the definition of different cases of plural nouns, per language. The amount of cases per noun may differ between language families, as does the expression to transform a number associated with a noun into a case id. Two attributes for the messages XML element configure the plural support:

Using WString::trn(), you can pass the count n that is used to select a suitable plural case.

As an example, consider an XML resource file describing Polish translations, which enlists all plural cases of the noun 'plik' (file in Polish). The noun is used this way:

<?xml version="1.0" encoding="UTF-8"?>
  <messages nplurals="3" 
            plural="n==1 ? 0 : n%10>=2 && n%10<=4 && (n%100<10 || n%100>=20) ? 1 : 2">

    <message id="file">
      <plural case="0">{1} plik</plural>
      <plural case="1">{1} pliki</plural>
      <plural case="2">{1} pliko'w</plural>
    </message>

  </messages>

To message defined in this resource file can then be used using WString::trn("file", n).

See also
WApplication::locale(), WString::tr(), WString::trn()

Member Function Documentation

void Wt::WMessageResourceBundle::hibernate ( )
virtual

Purges memory resources, if possible.

This is called afer event handling, and is an opportunity to conserve memory inbetween events, by freeing memory used for cached key/value bindings, if applicable.

The default implementation does nothing.

Reimplemented from Wt::WLocalizedStrings.

const std::set< std::string > Wt::WMessageResourceBundle::keys ( WFlags< Scope scope) const

Returns a set of all keys in this bundle.

Returns a set of all keys connected with this WMessageResources, within the scope provided as parameter.

void Wt::WMessageResourceBundle::refresh ( )
virtual

Rereads the message resources.

Purge any cached key/values, if applicable.

The default implementation does nothing.

Reimplemented from Wt::WLocalizedStrings.

bool Wt::WMessageResourceBundle::resolveKey ( const std::string &  key,
std::string &  result 
)
virtual

Resolves a key in the current locale.

This method is used by WString to obtain the UTF8 value corresponding to a key in the current locale.

Returns true if the key could be resolved. The value is written in result, encoded using UTF8.

See also
WApplication::locale(), WString::tr()

Implements Wt::WLocalizedStrings.

bool Wt::WMessageResourceBundle::resolvePluralKey ( const std::string &  key,
std::string &  result,
::uint64_t  amount 
)
virtual

Resolves the plural form of a key in the current locale.

This method is used by WString to obtain the UTF8 value corresponding to a key in the current locale, taking into account the possibility of multiple plural forms, and chosing the right plural form based on the amount passed.

Throws a std::logic_error if the underlying implementation does not provide support for plural internationalized strings.

Returns true if the key could be resolved. The value is written in result, encoded as UTF8.

See also
WApplication::locale(), WString::trn()

Reimplemented from Wt::WLocalizedStrings.

void Wt::WMessageResourceBundle::use ( const std::string &  path,
bool  loadInMemory = true 
)

Adds a (series) of message resource files to be used.

The path is not a URI, and relative paths will be resolved with respect to the working directory of the server. The XML files do not need to be deployed in the web server's docroot.

When you give as path: /path/to/name, then the following message resource files will be used:

  • /path/to/name.xml (default, English)
  • /path/to/name_nl.xml (for Dutch)
  • /path/to/name_fr.xml (for French)
  • etc...

The message file that is used depends on the application's locale.

See also
WApplication::locale()

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