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# QTranslator Class Reference

The QTranslator class provides internationalization support for text output. More...

    #include <QTranslator>

Inherits QObject.

- List of all members, including inherited members
- Obsolete members
- Compatibility members

### Public Types

- enum SaveMode { Everything, Stripped }

### Writable Properties

- 1 writable property inherited from QObject

### Public Functions

- QTranslator ( QObject * parent = 0 )
- ~QTranslator ()
- void clear ()
- bool contains ( const char * context, const char * sourceText, const char * comment = 0 ) const
- virtual QTranslatorMessage findMessage ( const char * context, const char * sourceText, const char * comment = 0 ) const
- void insert ( const QTranslatorMessage & message )
- bool isEmpty () const
- bool load ( const QString & filename, const QString & directory = QString::null, const QString & search_delimiters = QString::null, const QString & suffix = QString::null )
- bool load ( const uchar * data, int len )
- QList<QTranslatorMessage> messages () const
- void remove ( const QTranslatorMessage & message )
- bool save ( const QString & filename, SaveMode mode = Everything )
- void squeeze ( SaveMode mode = Everything )
- void unsqueeze ()

- 26 public functions inherited from QObject

### Public Slots

- 1 public slot inherited from QObject

### Signals

- 1 signal inherited from QObject

### Static Public Members

- 4 static public members inherited from QObject

### Protected Functions

- 7 protected functions inherited from QObject

## Detailed Description

The QTranslator class provides internationalization support for text output.

An object of this class contains a set of QTranslatorMessage objects, each of which specifies a translation from a source language to a target language. QTranslator provides functions to look up translations, add new ones, remove them, load and save them, etc.

The most common use of QTranslator is to: load a translator file created with Qt Linguist, install it using QApplication::installTranslator(), and use it via QObject::tr(). For example:

        int main(int argc, char ** argv)
        {
            QApplication app(argc, argv);

            QTranslator translator(0);
            translator.load("french.qm", ".");
            app.installTranslator(&translator);

            MyWidget m;
            app.setMainWidget(&m);
            m.show();

            return app.exec();
        }

Note that the translator must be created before the application's main window.

Most applications will never need to do anything else with this class. The other functions provided by this class are useful for applications that work on translator files.

We call a translation a "messsage". For this reason, translation files are sometimes referred to as "message files".

It is possible to lookup a translation using findMessage() (as tr() and QApplication::translate() do) and contains(), to insert a new translation messsage using insert(), and to remove one using remove().

Translation tools often need more information than the bare source text and translation, for example, context information to help the translator. But end-user programs that are using translations usually only need lookup. To cater for these different needs, QTranslator can use stripped translator files that use the minimum of memory and which support little more functionality than findMessage().

Thus, load() may not load enough information to make anything more than findMessage() work. save() has an argument indicating whether to save just this minimum of information or to save everything.

"Everything" means that for each translation item the following information is kept:

- The translated text - the return value from tr().
- The input key:
  - The source text - usually the argument to tr().
  - The context - usually the class name for the tr() caller.
  - The comment - a comment that helps disambiguate different uses of the same text in the same context.

The minimum for each item is just the information necessary for findMessage() to return the right text. This may include the source, context and comment, but usually it is just a hash value and the translated text.

For example, the "Cancel" in a dialog might have "Anuluj" when the program runs in Polish (in this case the source text would be "Cancel"). The context would (normally) be the dialog's class name; there would normally be no comment, and the translated text would be "Anuluj".

But it's not always so simple. The Spanish version of a printer dialog with settings for two-sided printing and binding would probably require both "Activado" and "Activada" as translations for "Enabled". In this case the source text would be "Enabled" in both cases, and the context would be the dialog's class name, but the two items would have disambiguating comments such as "two-sided printing" for one and "binding" for the other. The comment enables the translator to choose the appropriate gender for the Spanish version, and enables Qt to distinguish between translations.

Note that when QTranslator loads a stripped file, most functions do not work. The functions that do work with stripped files are explicitly documented as such.

QApplication::removeTranslator() QObject::tr() QApplication::translate()

See also QTranslatorMessage and QApplication::installTranslator().

## Member Type Documentation

### enum QTranslator::SaveMode

This enum type defines how QTranslator writes translation files. There are two modes:

`QTranslator::Everything` | files are saved with all available information
`QTranslator::Stripped` | files are saved with just enough information for end-user applications

Note that when QTranslator loads a stripped file, most functions do not work. The functions that do work with stripped files are explicitly documented as such.

## Member Function Documentation

### QTranslator::QTranslator ( QObject * parent = 0 )

Constructs an empty message file object with parent parent that is not connected to any file.

### QTranslator::~QTranslator ()

Destroys the object and frees any allocated resources.

### void QTranslator::clear ()

Empties this translator of all contents.

This function works with stripped translator files.

### bool QTranslator::contains ( const char * context, const char * sourceText, const char * comment = 0 ) const

Returns true if this message file contains a message with the key (context, sourceText, comment); otherwise returns false.

This function works with stripped translator files.

(This is is a one-liner that calls findMessage().)

### QTranslatorMessage QTranslator::findMessage ( const char * context, const char * sourceText, const char * comment = 0 ) const `[virtual]`

Returns the QTranslatorMessage for the key (context, sourceText, comment). If none is found, also tries (context, sourceText, "").

### void QTranslator::insert ( const QTranslatorMessage & message )

Inserts message into this message file.

This function does not work with stripped translator files. It may appear to, but that is not dependable.

See also remove().

### bool QTranslator::isEmpty () const

Returns true if this translator is empty, otherwise returns false. This function works with stripped and unstripped translation files.

### bool QTranslator::load ( const QString & filename, const QString & directory = QString::null, const QString & search_delimiters = QString::null, const QString & suffix = QString::null )

Loads filename + suffix (".qm" if the suffix is not specified), which may be an absolute file name or relative to directory. The previous contents of this translator object is discarded.

If the file name does not exist, other file names are tried in the following order:

1. File name without suffix appended.
2. File name with text after a character in search_delimiters stripped ("_." is the default for search_delimiters if it is an empty string) and suffix.
3. File name stripped without suffix appended.
4. File name stripped further, etc.

For example, an application running in the fr_CA locale (French-speaking Canada) might call load("foo.fr_ca", "/opt/foolib"). load() would then try to open the first existing readable file from this list:

1. /opt/foolib/foo.fr_ca.qm
2. /opt/foolib/foo.fr_ca
3. /opt/foolib/foo.fr.qm
4. /opt/foolib/foo.fr
5. /opt/foolib/foo.qm
6. /opt/foolib/foo

See also save().

### bool QTranslator::load ( const uchar * data, int len )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Loads the .qm file data data of length len into the translator.

The data is not copied. The caller must be able to guarantee that data will not be deleted or modified.

### QList<QTranslatorMessage> QTranslator::messages () const

Returns a list of the messages in the translator. This function is rather slow. Because it is seldom called, it's optimized for simplicity and small size, rather than speed.

If you want to iterate over the list, you should iterate over a copy, e.g.

        QList<QTranslatorMessage> list = myTranslator.messages();
        QList<QTranslatorMessage>::Iterator it = list.begin();
        while (it != list.end()) {
            process_message(*it);
            ++it;
        }

### void QTranslator::remove ( const QTranslatorMessage & message )

Removes message from this translator.

This function works with stripped translator files.

See also insert().

### bool QTranslator::save ( const QString & filename, SaveMode mode = Everything )

Saves this message file to filename, overwriting the previous contents of filename. If mode is `Everything` (the default), all the information is preserved. If mode is `Stripped`, any information that is not necessary for findMessage() is stripped away.

See also load().

### void QTranslator::squeeze ( SaveMode mode = Everything )

Converts this message file to the compact format used to store message files on disk.

You should never need to call this directly; save() and other functions call it as necessary. mode is for internal use.

See also save() and unsqueeze().

### void QTranslator::unsqueeze ()

Converts this message file into an easily modifiable data structure, less compact than the format used in the files.

You should never need to call this function; it is called by insert() and friends as necessary.

See also squeeze().