Perl 学习手札之十四： Module

Modules are collections of Perl code for use with different scripts

Modules can be object-oriented or procedural

Modules can contain code and/or data

Object-oriented vs procedural modules

 Most modules are object-oriented.

 object-oriented code has these properties.

 -Dynamic: the object determines what code to invoke

 -Encapsulated: the object contains all the code and data it needs

 -Abstraction: the details may be hidden from the user

 -Inheritance: One object may inherit properties from another

Procedural code has these properties:

 -simplicity: small subroutines may be coded quickly and easily

 -Modularity: Functionalities may be used and resused

 -Linearity: code is clear and readable

建立一个module：Example.pm

#Example.pm
#  Example perl module
#

package Example;
use strict;
use warnings;
use IO::File;

our $VERSION = "0.1";

sub new{
    my $class = shift;
    my $self = {};
    bless($self,$class);
    return $self;
}

sub copyfile
{ 
    my ( $self, $origfile, $newfile ) = @_;
    my $bufsize = 1024 * 1024;

    my $origfh = IO::File->new($origfile, 'r') or die("cannot open $origfile ($!)");
    my $newfh = IO::File->new($newfile, 'w') or die("cannot open $newfile ($!)");

    $origfh->binmode(":raw");
    $newfh->binmode(":raw");

    my $buf = '';
    while( $origfh->read( $buf, $bufsize ) ) {
        $newfh->print( $buf ); 
    }
    return 1;
}

1;

 这个就是前面的复制文件的代码，现在写到模块里面，注意package关键字。

下面就是调用模块的代码：

creating.pl

#!/usr/bin/perl
#
use strict;
use warnings;
use Example;

main(@ARGV);

sub main
{
    my $o = Example->new();
    $o->copyfile("olives.jpg","newfile.jpg");
    message("Done.");
}

sub message
{
    my $m = shift or return;
    print("$m\n");
}

sub error
{
    my $e = shift || 'unkown error';
    print("$0: $e\n");
    exit 0;
}

 如前面所示：用了module，代码变得非常简洁，并且可以复用。

下面写一个模块：

Artist.pm

# Artist.pm
# 
# Description goes here
# by Your Name
#

package Artist;
use strict;
use warnings;

our $VERSION = "0.1";

sub new
{
    my $class = shift;
    my $self  = {};

    bless( $self, $class );
    return $self;
}

sub name 
{
    my ($self,$name) = @_;
    $self->{name}=$name if defined $name;
    return $self->{name};
}

1;

__END__

=head1 NAME

Template - Description goes here

=head1 SYNOPSIS

    use Template
    my $o = Template->new;

=head1 METHODS

=over 4

=item B<new>

Constructs a new Template object. 

Returns a blessed Template object reference.

=item B<method>

Describe the method here 

=back

=head1 AUTHOR

Written by Your Name

=head1 HISTORY

    Version history here. 

=cut

 在__END__后面的部分是模块的注释。可以根据这个例子学习模块的编写

 然后调用模块：

oodata.pl

#!/usr/bin/perl
#
use strict;
use warnings;
use Artist;

main(@ARGV);

sub main
{
    my $o = Artist->new;
    my $o2=Artist->new;
    $o->name("Jimi Hendrix");
    $o2->name("Miles Davis");
    message($o->name);
    message($o2->name);
    message($Artist::VERSION);
    message($o->VERSION);
}

sub message
{
    my $m = shift or return;
    print("$m\n");
}

sub error
{
    my $e = shift || 'unkown error';
    print("$0: $e\n");
    exit 0;
}

 可以有几种方式初始化模块，然后调用模块。

 安装模块

1. 可以在unix-like系统里面采用下面的方式：

  1）：在命令行里面输入：sudo cpan 模块名

  2）：在命令行里面输入perl -MCPAN -e shell， 然后进入CPAN>模式，输入install 模块名，完成安装。

  3) ：在search.cpan.org里面查找模块，下载相应的tar.gz安装包，然后依次输入：

       perl MAKEFILE.pl 

       make

       make test

       make install

       然后完成安装。

2. 可以在windows系统下面采用下面的方式：

选择active perl->perl package manager来在图形界面下选择相应的安装包安装升级

 注意dependance