Difference between revisions of "Perl 101 for EPrints"
m (WIP get_config. I need to reword this) |
m (mention get_config is a wrapper) |
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==== Usage of get_config ==== | ==== Usage of get_config ==== | ||
| − | EPrints::Repository::get_config (accessed via $session->get_repository->get_conf()) can be used with two or three parameters | + | EPrints::Repository::get_config (accessed via $session->get_repository->get_conf()) can be used with two or three parameters. |
With only two (key and value) returns a hash | With only two (key and value) returns a hash | ||
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| − | + | get_config is a thin wrapper around config() | |
See also "perl_lib/EPrints/Repository.pm" line 1611 | See also "perl_lib/EPrints/Repository.pm" line 1611 | ||
Revision as of 01:59, 18 September 2018
Contents
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, $arg2)
Class::function($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) = @_;
Tips and tricks
Creating a session
Creating a session with eprints is now done via EPrints->new() however many scripts (and examples still use the legacy EPrints::Session->new() interface.
See "perl_lib/EPrints/BackCompatibility.pm" line 424 for details of the compatibility wrapper and "perl_lib/EPrints.pm" for full usage of Eprints methods.
Old style:
# When using this interface both values are required - 1 (to indicate this is a script not CGI) and repo id (second val). Attempting to run without the repo ID results in the following errors: # Use of uninitialized value $repository_id in string eq at /usr/share/eprints/perl_lib/EPrints.pm line 551. # Can't call method "get_database" on an undefined value at /usr/share/eprints/perl_lib/EPrints/DataObj.pm line 132. my $session = EPrints::Session->new( 1, 'REPOID');
New style:
# Note specifying CGI is not required via this interface. my $ep = EPrints->new( cleanup=>0 ); my $session = $ep->repository( 'epprod');
Usage of get_config
EPrints::Repository::get_config (accessed via $session->get_repository->get_conf()) can be used with two or three parameters.
With only two (key and value) returns a hash $session->get_repository->get_conf( "datacitedoi", "typesallowed")
With three values (key and two values) will return 1 (true) if the last item is found in the list of the second entry - config_entry below $session->get_repository->get_conf( "datacitedoi", "config_entry", 'Thesis')
get_config is a thin wrapper around config()
See also "perl_lib/EPrints/Repository.pm" line 1611
A basic EPrint extracting script
The simplest of examples, use eprints to register a session in the repository then read an (arbitrary) eprint; accessing two bits of information about it. The attributes accessed come from EPrint Object and API:EPrints/DataObj.
#!/usr/bin/perl -w use EPrints; use strict; # Create new session for interacting with eprints my $ep = EPrints->new( cleanup=>0 ); my $session = $ep->repository( 'REPOID'); my $id = 23743; # Create new object referency thing for our desired eprint (23743) $::pulled_eprint = EPrints::DataObj::EPrint->new( $session, $id ); print $::pulled_eprint->get_dataset_id . "\n"; print $::pulled_eprint->get_type . "\n"; $session->terminate();
This example can be expanded to test work in progress functions as required.
