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