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Re: Tieing and Blessing

by anazawa (Scribe)
on Oct 05, 2012 at 13:38 UTC ( #997477=note: print w/ replies, xml ) Need Help??


in reply to Tieing and Blessing

I posted similar question before. See also "Blessing tied hash".

By the way, tie() is one of my favorite functions. Tie::ToObject interests me specially.


Comment on Re: Tieing and Blessing
Re^2: Tieing and Blessing
by anaconda_wly (Scribe) on Jan 07, 2013 at 09:24 UTC
    I have the question is that firstly I didn't use DBM file yet and can't understand tie from its manual since lack the experience of dbm file. I think blessing is tieing a reference to a package actually.
      Though I don't understand how tie() works, too, I know how to use it ;) The following class represents a hash whose keys are case-insensitive:
      package Insensitive::Hash; use strict; use warnings; sub new { my ( $class, @args ) = @_; my %self; while ( my ($key, $value) = splice @args, 0, 2 ) { $self{ lc $key } = $value; } bless \%self, $class; } sub get { my ( $self, $key ) = @_; $self->{ lc $key }; } sub set { my ( $self, $key, $value ) = @_; $self->{ lc $key } = $value; } 1;
      How can we use Insensitive::Hash?
      use strict; use warnings; use Insensitive::Hash; my $hash = Insensitive::Hash->new( 'Content-Type' => 'text/plain', ); # $key is case-insensitive $hash->get( 'Content-Type' ); # => "text/plain" $hash->get( 'content-type' ); # => "text/plain" $hash->set( 'CONTENT-TYPE' => 'text/html' );
      To implement tie() interface, rename the method names of Insensitive::Hash as follows:
      package Insensitive::Hash; use strict; use warnings; # new -> TIEHASH # get -> FETCH # set -> STORE sub TIEHASH { my ( $class, @args ) = @_; my %self; while ( my ($key, $value) = splice @args, 0, 2 ) { $self{ lc $key } = $value; } bless \%self, $class; } sub FETCH { my ( $self, $key ) = @_; $self->{ lc $key }; } sub STORE { my ( $self, $key, $value ) = @_; $self->{ lc $key } = $value; } 1;
      How tie() works?
      use strict; use warnings; use Insensitive::Hash; tie my %hash, 'Insensitive::Hash', ( 'Content-Type' => 'text/plain' ); # <=> my $hash = Insensitive::Hash->TIEHASH( ... ) $hash{'Content-Type'}; # <=> $hash->FETCH( 'Content-Type' ); $hash{'content-type'}; # <=> $hash->FETCH( 'content-type' ); $hash{'CONTENT-TYPE'} = 'text/html'; # <=> $hash->STORE( 'CONTENT-TYPE' => 'text/html' );
      Insensitive::Hash was taken from "Object-oriented Perl" written by D. Conway. See also HTTP::Headers (field names are case-insensitive).

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