Moose Best Practices
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Moose Best Practices

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This presentation was created for, and presented at, the August 11th Thousand Oaks Perl Mongers meeting.

This presentation was created for, and presented at, the August 11th Thousand Oaks Perl Mongers meeting.

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    Moose Best Practices Moose Best Practices Presentation Transcript

    • MooseBest Practices
      by Aran Deltac (CPAN: bluefeet)
    • make_immutable()
      package MyClass;
      use Moose;

      __PACKAGE__->meta->make_immutable;
      1;
    • default => $value
      has ‘is_clean’ => (
      is => ‘ro’,
      isa => ‘Bool’,
      default => 1,
      );
    • Many Possible States
      has ‘ages’ => (
      is => ‘rw’,
      isa => ‘ArrayRef’,
      );
      sub avg_age {
      my ($self) = @_;
      my $ages = $self->ages();
      return (sum @$ages ) /
      scalar @$ages;
      }
      Possible States:
      undef
      []
      [ … ]
      if (defined($ages) and @$ages) { … }
    • Many Possible States
      has ‘ages’ => (
      is => ‘rw’,
      isa => ‘ArrayRef’,
      default => sub{ [] },
      );
      sub avg_age {
      my ($self) = @_;
      my $ages = $self->ages();
      return (sum @$ages ) /
      scalar @$ages;
      }
      Possible Values:
      undef
      []
      [ … ]
      if (@$ages) { … }
    • required => 1
      has ‘ssn’ => (
      is => ‘ro’,
      isa => ‘Str’,
      required => 1,
      );
    • Many Possible States
      subtype ‘NonEmptyArrayRef'
      => as ‘ArrayRef’
      => where { @$_ > 0 };
      has ‘ages’ => (
      is => ‘rw’,
      isa => ‘NonEmptyArrayRef’,
      required => 1,
      );
      sub avg_age {
      my ($self) = @_;
      my $ages = $self->ages();
      return (sum @$ages ) /
      scalar @$ages;
      }
      Possible Values:
      undef
      []
      [ … ]

    • builder => $sub_name
      has ‘dbh’ => (
      is => ‘ro’,
      isa => ‘dbh’,
      builder => ‘_build_dbh’,
      );
      sub _build_dbh {
      return DBI->connect(…);
      }
    • lazy => $bool
      has ‘dbh’ => (
      is => ‘ro’,
      isa => ‘dbh’,
      builder => ‘_build_dbh’,
      lazy => 1,
      );
      sub _build_dbh {
      return DBI->connect(…);
      }
    • lazy_build => 1
      has ‘dbh’ => (
      is => ‘ro’,
      isa => ‘DBI::db’,
      lazy_build => 1,
      );
      sub _build_dbh {
      return DBI->connect( … );
      }
    • is => ‘ro’
      has ‘name’ => (
      is => ‘ro’,
      isa => ‘Str’,
      );
    • Changing State
      has ‘ages’ => (
      is => ‘rw’,
      isa => ‘ArrayRef’,
      default => sub{ [] },
      );
      has ‘avg_age’ => (
      is => ‘ro’,
      isa => ‘Int’,
      lazy_build => 1,
      );
      sub _build_avg_age {
      my ($self) = @_;
      my $ages = $self->ages();
      return (sum @$ages ) /
      scalar @$ages;
      }
      my $obj = Class->new(
      ages => [4, 7],
      );
      print $obj->avg_age(); # 6
      $obj->ages([4, 11]);
      print $obj->avg_age(); # 6!
    • Changing State
      has ‘ages’ => (
      is => ‘ro’,
      isa => ‘ArrayRef’,
      default => sub{ [] },
      );
      has ‘avg_age’ => (
      is => ‘ro’,
      isa => ‘Int’,
      lazy_build => 1,
      );
      sub _build_avg_age {
      my ($self) = @_;
      my $ages = $self->ages();
      return (sum @$ages ) /
      scalar @$ages;
      }
      my $obj = Class->new(
      ages => [4, 7],
      );
      print $obj->avg_age(); # 6
      $obj->ages([4, 11]);
      print $obj->avg_age(); # 6!
    • writer => $sub_name
      has ‘color’ => (
      is => ‘ro’,
      isa => ‘Str’,
      write => ‘_color’,
      );
    • init_arg => undef
      has ‘result’ => (
      is => ‘ro’,
      isa => ‘HashRef’,
      writer => ‘_set_result’,
      init_arg => undef,
      );