tom arnall am Sonntag, 30. April 2006 22.57:
[...]
> OK, the above stuff is all good. and now i have another question. the
> following code:
>
> #!/usr/bin/perl -w
> use strict;
> use Tie::Scalar;
> use DB_File;
>
> my ($f,@f,%f);
>
> tie %f, "DB_File", "file.txt" ;
> $f{'a'}='aaaa';
> untie %f;
> %f = ();
> tie %f, "DB_File", "file.txt" ;
> @f = %f;
> print "
> @f";
>
> tie $f,"Tie::StdScalar","scalar.txt","\$f";
> $f = 'a';
> untie $f;
> $f = '';
> tie $f,"Tie::StdScalar","scalar.txt","\$f";
> print "
> $f
> ";
>
>
> produces:
>
> a aaaa
> scalar.txt
Hello tom
Since I'm not enough experienced with tie'ing, I can only provide a very basic
and hopefully correct answer:
> shouldn't the second line be 'a', i.e., shouldn't 'StdScalar' work along
> the lines of the code handling the tied hash variable?
When you look at the source of the Tie::StdScalar package, you can see that
the TIESCALAR method just blesses a reference to the string 'scalar.txt' to
the Tie::StdScalar class, FETCH gets the string, and STORE sets it.
(further arguments, as "\$f" - the same as '$f' btw - above, are ignored).
The class does not know that you want to treat 'scalar.txt' as a filename, and
therefore no persistent storage is involved, and thus the change done by $f =
'a' is lost after untie'ing.
> if this is not true,
> is there a module that does work similarly to 'DB_File', i.e., one that
> enables tie-ing a text file to a scalar?
I don't know. Maybe you want to look at Tie::File to access the lines of a
disk file via an array, search on search.cpan.org, or write your own subclass
to get the desired behaviour (I can't see much sense in using Tie::StdScalar
directly).
Dani
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