Bind a variable to an object class

Daftar Isi

• tie VARIABLE,CLASSNAME,LIST

  This function binds a variable to a package class that will provide theimplementation for the variable. VARIABLE is the name of the variableto be enchanted. CLASSNAME is the name of a class implementing objectsof correct type. Any additional arguments are passed to the newmethod of the class (meaning TIESCALAR, TIEHANDLE, TIEARRAY,or TIEHASH). Typically these are arguments such as might be passedto the dbm_open() function of C. The object returned by the newmethod is also returned by the tie function, which would be usefulif you want to access other methods in CLASSNAME.

  Note that functions such as keys and values may return huge listswhen used on large objects, like DBM files. You may prefer to use theeach function to iterate over such. Example:

   # print out history file offsets
   
   use NDBM_File;
   
   tie(%HIST, 'NDBM_File', '/usr/lib/news/history', 1, 0);
   
   while (($key,$val) = each %HIST) {
   
   print $key, ' = ', unpack('L',$val), "\n";
   
   }
   
   untie(%HIST);
   

  A class implementing a hash should have the following methods:

   TIEHASH classname, LIST
   
   FETCH this, key
   
   STORE this, key, value
   
   DELETE this, key
   
   CLEAR this
   
   EXISTS this, key
   
   FIRSTKEY this
   
   NEXTKEY this, lastkey
   
   SCALAR this
   
   DESTROY this
   
   UNTIE this
   

  A class implementing an ordinary array should have the following methods:

   TIEARRAY classname, LIST
   
   FETCH this, key
   
   STORE this, key, value
   
   FETCHSIZE this
   
   STORESIZE this, count
   
   CLEAR this
   
   PUSH this, LIST
   
   POP this
   
   SHIFT this
   
   UNSHIFT this, LIST
   
   SPLICE this, offset, length, LIST
   
   EXTEND this, count
   
   DESTROY this
   
   UNTIE this
   

  A class implementing a filehandle should have the following methods:

   TIEHANDLE classname, LIST
   
   READ this, scalar, length, offset
   
   READLINE this
   
   GETC this
   
   WRITE this, scalar, length, offset
   
   PRINT this, LIST
   
   PRINTF this, format, LIST
   
   BINMODE this
   
   EOF this
   
   FILENO this
   
   SEEK this, position, whence
   
   TELL this
   
   OPEN this, mode, LIST
   
   CLOSE this
   
   DESTROY this
   
   UNTIE this
   

  A class implementing a scalar should have the following methods:

   TIESCALAR classname, LIST
   
   FETCH this,
   
   STORE this, value
   
   DESTROY this
   
   UNTIE this
   

  Not all methods indicated above need be implemented. See perltie,Tie::Hash, Tie::Array, Tie::Scalar, and Tie::Handle.

  Unlike dbmopen, the tie function will not use or require a modulefor you; you need to do that explicitly yourself. See DB_Fileor the Config module for interesting tie implementations.

  For further details see perltie, tied VARIABLE.