Difference between revisions of "Perl 101 for EPrints"

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(Retrieving data from a config file)
(Retrieving data from a config file)
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[[category:Documentation_Needed]]
 
[[category:Documentation_Needed]]
 +
 +
===Where to start===
 +
 +
Learning Perl: Helping you get started with Perl 5....
 +
http://learn.perl.org/
 +
 +
Perl Tutorials
 +
http://perldoc.perl.org/perl.html#Tutorials
  
 
===Recommended books for learning Perl===
 
===Recommended books for learning Perl===
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http://www.amazon.com/Intermediate-Perl-Randal-L-Schwartz/dp/1449393098/
 
http://www.amazon.com/Intermediate-Perl-Randal-L-Schwartz/dp/1449393098/
  
 
+
==Using Perl in EPrints==
  
 
===Retrieving data from a config file===
 
===Retrieving data from a config file===
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Example of a data config file under /cfg/cfg.d/example.pl
 
Example of a data config file under /cfg/cfg.d/example.pl
  
The data strucure is an array of hashes
+
The data structure is an array of hashes (http://perldoc.perl.org/perldsc.html#ARRAYS-OF-HASHES)
  
 
<source lang="perl">
 
<source lang="perl">
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</source>
 
</source>
  
In perl, <source lang="perl">$obj->function($arg1, $arg2)</source> is a semantically nicer way of saying <source lang="perl">Class::function($obj, $arg1,$arg2)</source>  
+
===Function parameters===
 +
In perl, the following: <source lang="perl">$obj->function($arg1, $arg2)</source> is equivalent to: <source lang="perl">Class::function($obj, $arg1,$arg2)</source>  
 
In the example above, when we call:
 
In the example above, when we call:
 
<source lang="perl">
 
<source lang="perl">
              my $tags = $plugin->generate_tag($eprint, $field_conf);
+
my $tags = $plugin->generate_tag($eprint, $field_conf);
 
</source>
 
</source>
 
It is equivalent to:
 
It is equivalent to:
 
<source lang="perl">
 
<source lang="perl">
              my $tags = Example::generate_tag($plugin, $eprint, $field_conf);
+
my $tags = Example::generate_tag($plugin, $eprint, $field_conf);
 +
</source>
 +
This explains the three parameters listed in the top of the generate_tag function definition:
 +
<source lang="perl">
 +
sub generate_tag {
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my ($plugin, $eprint, $field_conf) = @_;
 
</source>
 
</source>

Revision as of 17:57, 28 July 2015


Where to start

Learning Perl: Helping you get started with Perl 5.... http://learn.perl.org/

Perl Tutorials http://perldoc.perl.org/perl.html#Tutorials

Recommended books for learning Perl

Learning Perl, 6th Edition by Randal Schwartz, brian d foy, Tom Phoenix http://www.amazon.com/Learning-Perl-Randal-L-Schwartz/dp/1449303587

Programming Perl: Unmatched power for text processing and scripting Fourth Edition Edition by Tom Christiansen, brian d foy, Larry Wall, Jon Orwant http://www.amazon.com/Programming-Perl-Unmatched-processing-scripting/dp/0596004923/

Intermediate Perl Second Edition Edition by Randal L. Schwartz, brian d foy, Tom Phoenix http://www.amazon.com/Intermediate-Perl-Randal-L-Schwartz/dp/1449393098/

Using Perl in EPrints

Retrieving data from a config file

Example of a data config file under /cfg/cfg.d/example.pl

The data structure is an array of hashes (http://perldoc.perl.org/perldsc.html#ARRAYS-OF-HASHES)

$c->{etd_ms}->{fields} = [
	{ tagname => 'etd_ms:type', type=> 'constant', value => "Electronic Thesis or Dissertation" },
	{ tagname => 'etd_ms:degree', type => 'compound', parts => [
		{ tagname => 'etd_ms:name', type => 'simple_text', eprint_fieldname => 'thesis_degree_name' },
		{ tagname => 'etd_ms:level', type => 'simple_text', eprint_fieldname => 'thesis_type' },
		{ tagname => 'etd_ms:discipline', type => 'simple_text', eprint_fieldname => 'department' },
		{ tagname => 'etd_ms:grantor', type => 'simple_text', eprint_fieldname => 'institution' },
	] },
];

Retrieving values from this config file in an "Example" export plugin under /plugins/EPrints/Plugin/Export/example.pm

               package EPrints::Plugin::Export::Example;
               use EPrints::Plugin::Export;
               @ISA = ( "EPrints::Plugin::Export" );
               [...]
               my $fields = $session->get_conf('etd_ms','fields');					
               foreach my $field_conf (@{$fields})
		{
		   my $tags = $plugin->generate_tag($eprint, $field_conf);			
		   foreach my $tag (@{$tags})
		   {
					push @dcdata, ($tag) if $tag; 
		   }
		}

Supporting function that returns an arrayref

sub generate_tag {
	my ($plugin, $eprint, $field_conf) = @_;

	#Constant value
	if ($field_conf->{type} eq 'constant')
	{
		return $plugin->generate_constant_tag($eprint, $field_conf);
	}
}

Supporting function that generates a tag

sub generate_constant_tag{
	my ($plugin, $eprint, $field_conf) = @_;

	my $tag = $plugin->_simple_tag($field_conf, $field_conf->{value});
	return [ $tag ];
}

Function parameters

In perl, the following:

$obj->function($arg1, $arg2)

is equivalent to:

Class::function($obj, $arg1,$arg2)

In the example above, when we call:

my $tags = $plugin->generate_tag($eprint, $field_conf);

It is equivalent to:

my $tags = Example::generate_tag($plugin, $eprint, $field_conf);

This explains the three parameters listed in the top of the generate_tag function definition:

sub generate_tag {
my ($plugin, $eprint, $field_conf) = @_;