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Think about Loose Coupling

Re: Rosetta Dispatch Table

by duelafn (Parson)
on Nov 22, 2017 at 01:27 UTC ( #1203974=note: print w/replies, xml ) Need Help??

in reply to Rosetta Dispatch Table (Interview Question)

I do like the hash for clean and obvious enumeration, but I hate the explicit hash and typing key names more than once, so I tend to hide both declaration and invocation in subs:

#!/usr/bin/perl -s use strict; use warnings; use 5.014; our $h; sub callback; our %CALLBACKS; # Callback functions --------------------------------------- callback first => sub { my $z = shift; print "in first_callback, z=$z\n"; return 1; }; callback last => sub { my $z = shift; print "in last_callback, z=$z\n"; return 2; }; # Implementation of dispatch table ------------------------- # (You need to write this code) sub callback { my ($name, $cb) = @_; $CALLBACKS{$name} = $cb; } sub invoker { my ($name, $z) = @_; return -1 unless exists($CALLBACKS{$name}); $CALLBACKS{$name}->($z); } sub help { say "Available callbacks: @{[ sort keys %CALLBACKS ]}"; } # Main program for testing --------------------------------- exit help() if $h; for my $name ( "first", "last", "fred" ) { my $rc = invoker( $name, $name . '-arg' ); print "$name: rc=$rc\n"; }


$ perl /tmp/ -h Available callbacks: first last $ perl /tmp/ in first_callback, z=first-arg first: rc=1 in last_callback, z=last-arg last: rc=2 fred: rc=-1

Good Day,

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