Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

Trouble coercing array elements

by docdurdee (Beadle)
on Jul 28, 2011 at 20:13 UTC ( #917344=perlquestion: print w/ replies, xml ) Need Help??
docdurdee has asked for the wisdom of the Perl Monks concerning the following question:

My second post today! inspired by the first. I would like to set up an attribute that is an array of arrayrefs with coercion of nonarrayrefs to array refs. eg.

[ 0, [ 0, 0, 0 ], [1,2,3] ] into [ [0], [ 0, 0, 0 ], [1,2,3] ]

also, I'd like to be able to push or set elements to the AoA with coercion as well. Here is my attempt:

{ package MyArray; use namespace::autoclean; use Moose::Util::TypeConstraints; use Moose; subtype 'myarray' => as 'ArrayRef[Num|Str|Int]'; coerce 'myarray' => from 'Num|Str|Int' => via {[$_]}; has 'myarray' => ( traits => ['Array'], is => 'rw', isa => 'myarray', default => sub { [] }, handles => { push => 'push', get => 'get', set => 'set', elements => 'elements', count => 'count', }, coerce => 1, ); __PACKAGE__->meta->make_immutable; } use Modern::Perl; my $a0 = MyArray->new( myarray => [ 0, [ 0, 0, 0 ], [1,2,3] ] ) ; use Data::Dumper; print Dumper $a0; $a0->set(1,'cat'); print Dumper $a0; $a0->push(2.0); print Dumper $a0;

Comment on Trouble coercing array elements
Select or Download Code
Re: Trouble coercing array elements
by ikegami (Pope) on Jul 28, 2011 at 21:46 UTC

    [ The parent was crossposted on StackOverflow. ]

    Building on my StackOverflow answer (where I didn't handle the trait), here's one that does:

    { package MyArray; use namespace::autoclean; use Moose; use Moose::Util::TypeConstraints; subtype 'MyArray::Ents::Level2' => as 'ArrayRef[Str|Num|Int]'; coerce 'MyArray::Ents::Level2' => from 'Str|Num|Int' => via { [ $_ ] }; my $level2_constraint = Moose::Util::TypeConstraints::find_type_constraint( 'MyArray::Ents::Level2'); # Doesn't work if I remove this?!? subtype 'MyArray::Ents' => as 'ArrayRef[MyArray::Ents::Level2]'; coerce 'ArrayRef[MyArray::Ents::Level2]' => from 'ArrayRef[MyArray::Ents::Level2|Str|Num|Int]' => via { [ map $level2_constraint->coerce($_), @$_ ] }; no Moose::Util::TypeConstraints; has 'myarray' => ( traits => ['Array'], is => 'rw', isa => 'ArrayRef[MyArray::Ents::Level2]', default => sub { [] }, handles => { push => 'push', get => 'get', set => 'set', elements => 'elements', count => 'count', }, coerce => 1, ); no Moose; __PACKAGE__->meta->make_immutable; } use Modern::Perl; use Data::Dumper qw( Dumper ); sub dump_it { local $Data::Dumper::Useqq = 1; local $Data::Dumper::Terse = 1; local $Data::Dumper::Indent = 0; print(Dumper($_[0]), "\n"); } my $a0 = MyArray->new( myarray => [ 0, [ 0, 0, 0 ], [1,2,3] ] ) ; dump_it($a0); $a0->set(1, 'cat'); dump_it($a0); $a0->push(2.0); dump_it($a0);
    bless( {"myarray" => [[0],[0,0,0],[1,2,3]]}, 'MyArray' ) bless( {"myarray" => [[0],["cat"],[1,2,3]]}, 'MyArray' ) bless( {"myarray" => [[0],["cat"],[1,2,3],[2]]}, 'MyArray' )

    Unfortunately, the following is not compatible with the trait:

    subtype 'MyArray::Ents::Level2' => as 'ArrayRef[Str|Num|Int]'; coerce 'MyArray::Ents::Level2' => from 'Str|Num|Int' => via { [ $_ ] }; my $level2_constraint = Moose::Util::TypeConstraints::find_type_constraint( 'MyArray::Ents::Level2'); subtype 'MyArray::Ents' => as 'ArrayRef[MyArray::Ents::Level2]'; coerce 'MyArray::Ents' => from 'ArrayRef[MyArray::Ents::Level2|Str|Num|Int]' => via { [ map $level2_constraint->coerce($_), @$_ ] }; ... isa => 'MyArray::Ents'

    It results in:

    Can't call method "is_a_type_of" on an undefined value at .../Moose/Me +ta/Attribute/Native/Trait.pm line 98

    I don't like adding coercions to global types, although ArrayRef[MyArray::Ents::Level2] is not as global as others.

Re: Trouble coercing array elements
by docdurdee (Beadle) on Jul 29, 2011 at 13:17 UTC

    Thanks ikegami! Playing around with your code helped me learn this cool stuff. I soon realized that I wanted to leave both ArrayRef and Objects alone. Starting from ikegami's code, I added this, cleaned it up (I hope) and am posting it here for reference. Perl rocks! Moose rocks!

    { package MyArray; use namespace::autoclean; use Moose; use Moose::Util::TypeConstraints; subtype 'ValueOrObject' => as 'Value|Object'; subtype 'Inside::MyArray::Ents' => as 'ArrayRef[Value]|Object'; coerce 'Inside::MyArray::Ents' => from 'Value' => via { return [ $_ ] }; my $level2_constraint = Moose::Util::TypeConstraints::find_type_constraint( 'Inside::MyArray::Ents'); subtype 'MyArray::Ents' => as 'ArrayRef[Inside::MyArray::Ents]'; coerce 'MyArray::Ents' => from 'ArrayRef[Inside::MyArray::Ents|ValueOrObject]' => via { [ map $level2_constraint->coerce($_), @$_ ] }; has 'myarray' => ( traits => ['Array'], is => 'rw', isa => 'MyArray::Ents', default => sub { [] }, handles => { push => 'push', pop => 'pop', get => 'get', set => 'set', elements => 'elements', count => 'count', }, coerce => 1, ); __PACKAGE__->meta->make_immutable; } use Modern::Perl; use Math::VectorReal; my $a0 = MyArray->new( myarray => [ 0, [ 0, 0, 0 ], [1,2,3] ] ) ; use Data::Dumper; print Dumper $a0; $a0->set(1,'cat'); print Dumper $a0; $a0->push('dog'); print Dumper $a0; $a0->push('1.0'); print Dumper $a0; my $vec1 = vector(1,2,3); $a0->push($vec1); print Dumper $a0; my $vec3 = $a0->get(5); my $vec2 = $a0->pop; print Dumper $vec2; print Dumper $vec3; say $vec1-$vec2; 1;

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://917344]
Approved by Corion
Front-paged by Corion
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others contemplating the Monastery: (13)
As of 2014-07-31 19:46 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    My favorite superfluous repetitious redundant duplicative phrase is:









    Results (252 votes), past polls