Perl from the ground up: objects and testing

Perl From Ground level and Up Lecture 2 October 22 2007 By Shmuel Fomberg

Parameters Passing ,[object Object],October 22 2007 Shmuel Fomberg func(5, $x, (7, 4), [$y, %h]); # @_ = (5, $x, 7, 4, [$y, %h]) sub func { my $x1 = shift; # $x1 is 5 $_[0] = 3; # $x now is 3! (do not use this, normally) my ($x2, $x3) = @_; # multiple params …

Perl script life cycle ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],October 22 2007 Shmuel Fomberg

Perl script life cycle October 22 2007 Shmuel Fomberg #!/usr/bin/perl -w use strict; BEGIN {print "one "} use A; END {print "two "} print "three "; package A; BEGIN {print "four "} END {print "five "} print "six "; 1; # <- note here Output: one four six three two five Test.pl A.pm

What is a Class? ,[object Object],[object Object],October 22 2007 Shmuel Fomberg Class->func(…); my $name = ‘Class’; $name->func(…); In both cases: Class::func(‘Class’, …) Can even do: my $fname = ‘func’; $name->$fname(…);

What is a Class? October 22 2007 Shmuel Fomberg ,[object Object],[object Object],package Class; our $var = 5; … elsewhere in the program: print $Class::var;

Class inheritance ,[object Object],[object Object],October 22 2007 Shmuel Fomberg package Class; our @ISA = qw{ClassP1 ClassP2}; use base qw{ClassP1 ClassP2}; func(…); #will search … elsewhere in the program: Class->func(…); #will search Class::func(…); # will not search Class->ClassP2::func(…); # explicit

Class inheritance ,[object Object],October 22 2007 Shmuel Fomberg Class->can(‘func’); Class->isa(‘ClassP1); UNIVERSIAL::isa(‘Class’, ‘ClassP1’); ,[object Object],[object Object],[object Object],package Class; SubClass->SUPER::func(…);

The SUPER meta class October 22 2007 Shmuel Fomberg A B C D E $class->func(...) $class->SUPER::func(...) package C; sub mysub { my $class = shift; # $class eq ‘E’ …..

What is an Object? ,[object Object],[object Object],[object Object],[object Object],October 22 2007 Shmuel Fomberg my $self = bless {}, ‘Class’; ,[object Object],[object Object],my $self = shift; my ($self, $param1, …) = @_;

What is an Object? ,[object Object],October 22 2007 Shmuel Fomberg $obj->{var1} = 5; ,[object Object],$obj->isa(‘ClassP1’); if ref($obj) and $obj->isa(‘ClassP1’); $obj->func(…); $self->SUPER::func(…); Class::func($obj, …);

Creating an Object ,[object Object],October 22 2007 Shmuel Fomberg sub new { my ($class, params…) = @_; my $self = { keys and values… }; return bless $self, $class; } ,[object Object],sub new { my ($class, params…) = @_; $self = $class->Parent::new(params…); # do more initialization return $self; }

Destroying an Object ,[object Object],[object Object],[object Object],October 22 2007 Shmuel Fomberg sub DESTROY { my $self = shift; # do whatever $self->SUPER::DESTROY(); }

Problems? October 22 2007 Shmuel Fomberg NOT SCALABLE Object variable are just keys in hash - spelling error will created bugs You have to know and hard-code the Class-variable package The new will not support multi-inheritance

How Should it be done ,[object Object],October 22 2007 Shmuel Fomberg package Root; use base qw/Class::Accessor Class::Data::Inheritable/; sub new { my ($class, @params) = @_; my $self = bless {}, $class; $self->_Init(@params); return $self; } sub _Init {} sub DESTROY {}

How Should it be done ,[object Object],October 22 2007 Shmuel Fomberg package MyClass; use base qw/Root/; __PACKAGE__->mk_accessors(qw(name role salary)); sub _Init { my ($self, $salary, $name) = @_; $self->SUPER::_Init($name); $self->salary($salary); } sub DESTROY { # if needed my $self = shift; ... do something ... $self->SUPER::DESTORY; }

How Should it be done ,[object Object],October 22 2007 Shmuel Fomberg package MyClass; use base qw/Root/; Stuff->mk_classdata(‘Color'); # Declare the location of the data file for this class. Stuff->Color(‘blue'); # Or, all in one shot: Stuff->mk_classdata(Color => ‘blue');

Unit Test ,[object Object],[object Object],[object Object],[object Object],October 22 2007 Shmuel Fomberg 5 == sum(3,2)

Perl Standard Unit Test ,[object Object],October 22 2007 Shmuel Fomberg use Test::Simple tests => 2; my $foo = "x"; ok( $foo eq "x", 'foo is X' ); ok( $foo ne "Y", 'foo is not Y'); 1..2 ok 1 - foo is X ok 2 - foo is not Y

A bit more advanced techniques ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],October 22 2007 Shmuel Fomberg

Perl from the ground up: objects and testing

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