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Re^3: How to call a sub-routine ref

by tobyink (Abbot)
on Oct 22, 2012 at 12:33 UTC ( #1000320=note: print w/replies, xml ) Need Help??

in reply to Re^2: How to call a sub-routine ref
in thread How to call a sub-routine ref

use v5.14; use JSON -convert_blessed_universally; use Test::More; package Foo { sub new { bless \@_ => shift } sub bar { return JSON::to_json(\@_, { convert_blessed => 1, canoni +cal => 1 }) } } package Oof { our @ISA = 'Foo'; sub bar { scalar reverse JSON::to_json(\@_, { convert_blessed => 1 +, canonical => 1 }) } } # You are no doubt familiar with these... my $obj = Foo->new(1); # calling a class method (a constructor) my $str = $obj->bar; # calling an object method is($str, '[[1]]', 'bar returned what we expected'); # Did you know you could do this? my $constructor = 'new'; my $method = 'bar'; $obj = Foo->$constructor(1); $str = $obj->$method; is($str, '[[1]]', 'bar returned what we expected'); # We can even use fully qualified names... $constructor = 'Foo::new'; $method = 'Oof::bar'; $obj = Foo->$constructor(1); $str = $obj->$method; is($str, ']]1[[', 'Oof::bar is the stringy reverse of Foo::bar'); # Or we can use coderefs $constructor = \&Foo::new; $method = \&Oof::bar; $obj = Foo->$constructor(1); $str = $obj->$method; is($str, ']]1[[', 'Oof::bar is the stringy reverse of Foo::bar'); # Now, what is the point of blessing things? We bless objects # so that when we call $object->method, Perl "knows" what # package to find the method in. # # But if we can use coderefs as if they were methods, then # Perl doesn't really need the object to be blessed... # $method = \&Oof::bar; $obj = [1, 2, 3]; # a plain arrayref $str = $obj->$method; is($str, ']]3,2,1[[', 'Can call coderef methods on unblessed things'); # It even works with undef $method = \&Oof::bar; $obj = undef; $str = $obj->$method; is($str, ']llun[', 'llun is null backwards'); # A pair of parentheses evaluates the empty list in list # context, but undef in scalar context. The arrow operator # imposes a scalar context on the left-hand side. $method = \&Oof::bar; $str = ()->$method; is($str, ']llun[', 'llun is null backwards'); # do{} with nothing inside the block returns undef $method = \&Oof::bar; $str = do{}->$method; is($str, ']llun[', 'llun is null backwards'); # More fun... $method = \&Foo::bar; $str = do { my $x = 1; my $y = 2; $x+$y }->$method(2,1); is($str, '[3,2,1]', 'more fun'); # This makes sense when you consider what comma does in scalar context +... $method = \&Foo::bar; $str = (5,4,3)->$method(2,1); is($str, '[3,2,1]', 'maybe counter-intuitive'); done_testing();
perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

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Re^4: How to call a sub-routine ref
by grizzley (Chaplain) on Oct 23, 2012 at 07:28 UTC
    Thanks to you and Corion I have now much to meditate about!

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