tie - bind a variable to an object class

- NAME
- SYNOPSIS
- DESCRIPTION

# NAME

tie - bind a variable to an object class

# SYNOPSIS

tie VARIABLE,CLASSNAME,LIST

# DESCRIPTION

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`, `TIEHANDLE`, `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 lists when used on large objects, like DBM files. You may prefer to use the `each` 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 file handle 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 the perltie manpage, the Tie::Hash manpage, the Tie::Array manpage, the Tie::Scalar manpage, and the Tie::Handle manpage.

Unlike `dbmopen`, the `tie` function will not use or require a module for you--you need to do that explicitly yourself. See the DB_File manpage or the Config module for interesting `tie` implementations.

For further details see the perltie manpage, tied VARIABLE.

tie - bind a variable to an object class