[ новости /+++ | форум | теги | ]

                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.


NAME
     messages, messages_byname

      - Messaging facets.



SYNOPSIS
     #include<locale>
     class messages_base;
     template <class charT> class messages;



DESCRIPTION
     messages_gives access to a localized messaging facility. The
     messages   facet   is   used  with  the  "C"  locale,  while
     the_messages_byname facet is used with named locales.

     The messages_base class includes a catalog type for  use  by
     the derived messages and messages_byname classes.

     Note that the default messages facet uses catopen, catclose,
     etc.,  to  implement  the message database. If your platform
     does not support these, then you need to imbue your own mes-
     sages facet by implementing whatever database is available.



INTERFACE
     class messages_base {
     public:
      typedef int catalog;
     };

     template <class charT>
     class messages : public locale::facet, public  messages_base
     {
     public:
      typedef charT char_type;
      typedef basic_string<charT> string_type;
      explicit messages(size_t = 0);
      catalog open(const basic_string<char>&, const locale&)
                   const;
      string_type get(catalog, int, int,
                      const string_type&) const;
      void    close(catalog) const;
      static locale::id id;
     protected:
       ~messages();  // virtual
      virtual catalog do_open(const basic_string<char>&,
                              const locale&) const;
      virtual string_type do_get(catalog, int, int,
                                  const string_type&) const;
      virtual void    do_close(catalog) const;
     };

     class messages_byname : public messages<charT> {
     public:
      explicit messages_byname(const char*, size_t = 0);
     protected:
       ~messages_byname();  // virtual
      virtual catalog do_open(const basic_string<char>&,
                              const locale&) const;
     virtual string_type do_get(catalog, int, int,
                               const string_type&) const;
      virtual void    do_close(catalog) const;
     };



TYPES
     char_type


        Type of character the facet is instantiated on.



     string_type


        Type of character string returned by member functions.



CONSTRUCTORS
     explicit messages(size_t refs = 0)


        Constructs a messages facet. If the refs argument  is  0,
        then  destruction  of  the  object  is  delegated  to the
        locale, or locales, containing it. This allows  the  user
        to  ignore lifetime management issues. On the other hand,
        if refs is 1, then the object must be explicitly  deleted
        because the locale does not do so.



     explicit messages_byname(const char* name,
       size_t refs = 0);


        Constructs a messages_byname facet. Uses the named locale
        specified  by the name argument. The refs argument serves
        the same purpose as it does for the messages constructor.



DESTRUCTORS
     ~messages();  // virtual and protected


        Destroys the facet.



FACET ID
     static locale::id id;



        Unique identifier for this type of facet.



PUBLIC MEMBER FUNCTIONS
     The public members of the messages facet include  an  inter-
     face  to  protected  members.  Each  public member xxx has a
     corresponding virtual protected member do_xxx. All  work  is
     delegated  to  these  protected members.   For instance, the
     long version of the public open function  simply  calls  its
     protected cousin do_open.


     void
     close(catalog c) const;
     string_type
     get(catalog c, int set, int msgid,
        const string_type& dfault) const;

     catalog
     open(const basic_string<char>& fn, const locale&) const;


        Each of these public member functions xxx simply call the
        corresponding protected do_xxx function.



PROTECTED MEMBER FUNCTIONS
     virtual void
     do_close(catalog cat) const;


        Closes the catalog. The cat argument must be obtained  by
        a call to open().



     virtual string_type
     do_get(catalog cat, int set, int msgid,
           const string_type& dfault) const;


        Retrieves a specific message. Returns the message identi-
        fied by cat, set, msgid, and dfault. cat must be obtained
        by a previous call to open(). This function must  not  be
        called  with  a cat that has had close called on it after
        the last call to open(). That is,  the  catalog  must  be
        open and not yet closed.



     virtual catalog
     do_open(const  basic_string<char>&  name,   const   locale&)
     const;


        Opens a message catalog.  Returns  a  catalog  identifier
        that  can  be  passed  to  the get() function in order to
        access specific messages. Returns -1 if the catalog  name
        specified  in the name argument is invalid. The loc argu-
        ment is used for codeset conversion if necessary.



EXAMPLE
     //
     // messages.cpp
     //
     #include <string>
     #include <iostream>

     int main ()
     {
      using namespace std;

      locale loc;

       // Get a reference to the messages<char> facet
      const messages<char>& mess =
     #ifndef _RWSTD_NO_TEMPLATE_ON_RETURN_TYPE
        use_facet<messages<char> >(loc);
     #else
        use_facet(loc,(messages<char>*)0);
     #endif

       // Open a catalog and try to grab
       // both some valid messages, and an invalid message
      string def("Message Not Found");
      messages<char>::catalog cat =
              mess.open("./rwstdmessages.cat",loc);
      if (cat != -1)
       {
        string msg0 = mess.get(cat,1,1,def);
        string msg1 = mess.get(cat,1,2,def);
        string msg2 = mess.get(cat,1,6,def); // invalid msg #
        string msg3 = mess.get(cat,2,1,def);

        mess.close(cat);
        cout << msg0 << endl << msg1 << endl
              << msg2 << endl << msg3 << endl;
       }
      else
        cout << "Unable to open message catalog" << endl;

      return 0;
     }



SEE ALSO
     locale, facets

Партнёры:

Хостинг: