NAME
`overload::substr' - overload Perl's `substr()' function
SYNOPSIS
package My::Stringlike::Object;
use overload::substr;
sub _substr
{
my $self = shift;
if( @_ > 2 ) {
$self->replace_substr( @_ );
}
else {
return $self->get_substr( @_ );
}
}
...
DESCRIPTION
This module allows an object class to overload the `substr' core
function, which Perl's `overload' pragma does not allow by itself.
It is invoked similarly to the `overload' pragma, being passed a single
named argument which should be a code reference or method name to
implement the `substr' function.
use overload::substr substr => \&SUBSTR;
use overload::substr substr => "SUBSTR";
The referred method will be invoked as per core's `substr'; namely, it
will take the string to be operated on (which will be an object in this
case), an offset, optionally a length, and optionally a replacement.
$str->SUBSTR( $offset );
$str->SUBSTR( $offset, $length );
$str->SUBSTR( $offset, $length, $replacement );
In each case, whatever it returns will be the return value of the
`substr' function that invoked it.
If the `substr' argument is not provided, it defaults to a method called
`_substr'.
It is not required that the return value be a plain string; any Perl
value may be returned unmodified from the `substr' method, or passed in
as the value of the replacement. This allows objects to behave in
whatever way is deemed most appropriate.
TODO
* More testing - edge cases, especially in LVALUE logic.
* Test for memory leaks, especially in LVALUE logic.
* Look into / implement fixup of substr() ops compiled before
module is loaded
* Consider if implementations of split(), and `m//' and `s///'
regexps should be done that also uses the overloaded substr()
method.
ACKNOWLEDGEMENTS
With thanks to Matt S Trout <
[email protected]> for suggesting the
possibility, and Joshua ben Jore <
[email protected]> for the inspiration by
way of UNIVERSAL::ref.
AUTHOR
Paul Evans <
[email protected]>
