in reply to Error handling in chained method calls

Maybe a wrapper method $safecall is what you need, you can put all runtime checks needed in there.

Please note that arguments are optional and need to be passed as array_refs in order to be distinguished from methodnames.

$\="\n"; sub safecall{ db(@_); my $obj=shift; # TODO check object/class my ($meth,$a_args); while (@_){ $meth=shift; # TODO check method $a_args= (ref $_[0] eq "ARRAY" ? shift : []); $obj=$obj->$meth(@$a_args); # TODO check ret +urned obj } print "-"x20; return $obj; }; my $safecall=\&safecall; my $obj={}; bless $obj, CLASS; #- USAGE/INTERFACE - $obj->$safecall( "meth1" ); $obj->$safecall( meth1=> meth2=> [3,4,5] ); $obj->$safecall( qw(meth1 meth2) ); $obj->$safecall( meth1=>[1,2,3] , meth2=> [3,4,5] ); $obj->$safecall( meth1=>[1,2,3] ) -> meth2(3,4,5); # still possible safecall($obj, meth1=>[1,2,3] , meth2=> [3,4,5]); # fuctional appr +oach package CLASS; sub meth1 { my $self=shift; print "call meth1 with (@_)"; return $self; } sub meth2 { my $self=shift; print "call meth2 with (@_)"; return $self; }

OUTPUT:

call meth1 with () ---------- call meth1 with () call meth2 with (3 4 5) ---------- call meth1 with () call meth2 with () ---------- call meth1 with (1 2 3) call meth2 with (3 4 5) ---------- call meth1 with (1 2 3) ---------- call meth2 with (3 4 5)

Cheers Rolf

UPDATE: added functional approach.

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Re^2: Error handling in chained method calls
by LanX (Saint) on Oct 23, 2010 at 20:04 UTC
    Hm ...

    I'm not sure if it's worth it, but by applying Attribute::Handlers on safecall it could even be possible to run some checks at compile time.

    Maybe its better to rename $safecall to $CHAIN or $_chain to make the syntax "sweeter" and make conflicts unlikely if the $ is missing.

    $obj->$CHAIN( meth1=>[1,2,3] , meth2=>[3,4,5] );

    Cheers Rolf

    UPDATE: it should even be possible to add a method safecall to UNIVERSAL, to avoid always putting the $ in front, but I'm a little reluctant because of possible side effects.