perlfunc
gods
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tie - bind a variable to an object class
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tie
<FONT SIZE=-1>VARIABLE,CLASSNAME,LIST</FONT>
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This function binds a variable to a package class that will provide the implementation for the variable.
<FONT SIZE=-1>VARIABLE</FONT> is the name of the variable to be enchanted.
<FONT SIZE=-1>CLASSNAME</FONT> is the name of a class implementing objects of correct type. Any additional arguments are passed to the ``
<CODE>new()</CODE>'' method of the class (meaning <CODE>TIESCALAR</CODE>, <CODE>TIEARRAY</CODE>, or <CODE>TIEHASH</CODE>). Typically these are arguments such as might be passed to the <CODE>dbm_open()</CODE>
function of
<FONT SIZE=-1>C.</FONT> The object returned by the ``<CODE>new()</CODE>'' method is also returned by the [perlfunc:tie|tie()] function, which would be useful if you want to access other methods in
<FONT SIZE=-1>CLASSNAME.</FONT>
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Note that functions such as [perlfunc:keys|keys()] and [perlfunc:values|values()] may return huge lists when used on large objects, like
<FONT SIZE=-1>DBM</FONT> files. You may prefer to use the
[perlfunc:each|each()] function to iterate over such. Example:
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<PRE> # 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);
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<FONT SIZE=-1>A</FONT> class implementing a hash should have the following
methods:
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<PRE> TIEHASH classname, LIST
DESTROY this
FETCH this, key
STORE this, key, value
DELETE this, key
EXISTS this, key
FIRSTKEY this
NEXTKEY this, lastkey
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<FONT SIZE=-1>A</FONT> class implementing an ordinary array should have the
following methods:
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<PRE> TIEARRAY classname, LIST
DESTROY this
FETCH this, key
STORE this, key, value
[others TBD]
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<FONT SIZE=-1>A</FONT> class implementing a scalar should have the
following methods:
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<PRE> TIESCALAR classname, LIST
DESTROY this
FETCH this,
STORE this, value
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Unlike [perlfunc:dbmopen|dbmopen()], the [perlfunc:tie|tie()] function will not use or require a module for you--you need to do that
explicitly yourself. See [perlfunc:lib:DB_File|the DB_File manpage]
or the <EM>Config</EM> module for interesting [perlfunc:tie|tie()] implementations.
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For further details see [perlman:perltie|the perltie manpage], <U>tied VARIABLE</U>.
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