NAME

    Scalar::IfDefined - Apply block to scalar depending on if it's defined.

SYNOPSIS

        use Scalar::IfDefined qw/ifdef/;
    
        my $hash = {
            a => 1,
            b => 2,
            c => 3,
            d => {
                E => 1,
                F => 2,
            },
        };
    
        ifdef { $_ + 1 } $hash->{a};   # ---> 2
        ifdef { $_ + 1 } $hash->{missing};    # ---> undef
        ifdef { $_ + 1 } ifdef { $_->{F} } $hash->{d};  # ---> 3
        ifdef { $_ + 1 } ifdef { $_->{MISSING} } $hash->{d};  # ---> undef
    
    
        # Or perhaps with Perl6::Flows
    
        use Perl6::Flows;
        my $result = (
            $hash->{a} 
                ==> ifdef { $_->{F} }
                ==> ifdef { $_ + 1 }
        );            # ---> 3

EXPORT

    ifdef

    $ifdef

SUBROUTINES/METHODS

 ifdef

    Takes a block and a scalar value.

    If the scalar value is undef, the block is ignored and undef is
    returned straight away.

    If the scalar value is defined, then the block is evaluated with $_ as
    the value passed in, and the result of the block is returned.

 $ifdef

    Used to dereference a possibly-undef scalar.

    If the scalar is undef, returns undef.

    If the scalar is an object, the first argument is the method to call,
    and the rest of the arguments are the method arguments.

    If the scalar is an array ref, the first argument is used to index into
    the array.

    If the scalar is a hash ref, the first argument is used to access the
    hash.

    If the scalar is a code ref, the code ref is run with all the
    arguments.

    As a special case, if the first argument is a code ref, it will be run
    with the scalar as the first argument and the other arguments as the
    rest. This form allows you to use $ifdef on a simple scalar - but you
    might be better off with ifdef itself for that.

    The following uses will all return undef if the $scalar is undef, or
    The Right Thing if not.

        # Run "method_name" on $obj, if $obj is defined.
        $obj->$ifdef("method_name", "argument", "argument");
    
        # Run $coderef with two arguments if $coderef is defined.
        $coderef->$ifdef("argument", "argument");
    
        # Lowercase the zeroth element of the arrayref, or undef if either of those
        # things is undef.
        $arrayref->$ifdef(0)->$ifdef(sub { lc });
    
        # Call "method_name" on $hashref->{object}, or return undef if either of
        # those is undef
        $hashref->$ifdef('object')->$ifdef('method_name');

AUTHOR

    Nick Booker, <NMBooker at gmail.com>

BUGS

    https://github.com/nmbooker/p5-Scalar-IfDefined/issues

ACKNOWLEDGEMENTS

 Alastair McGowan-Douglas (ALTREUS)

    For developing the $ifdef (coderef) form.

LICENSE AND COPYRIGHT

    Copyright (C) 2015 Nick Booker

    This program is free software; you can redistribute it and/or modify it
    under the terms of either: the GNU General Public License as published
    by the Free Software Foundation; or the Artistic License.

    See http://dev.perl.org/licenses/ for more information.

