# marc4j4r

A ruby wrapper around the marc4j.jar (as forked by javamarc) java library for dealing with library MARC data.

## Getting a MARC reader

marc4j4r provides three readers out of the box: :strictmarc (binary), :permissivemarc (:binary), and :marcxml (MARC-XML).
You can pass either a filename or an open IO object (either ruby or java.io.inputstream)

    require 'marc4j4r'
  
    binreader = MARC4J4R::Reader.new('test.mrc') # defaults to :strictmarc
    binreader = MARC4J4R::Reader.new('test.mrc', :strictmarc)
  
    permissivereader =  MARC4J4R::Reader.new('test.mrc', :permissivemarc)

    xmlreader = MARC4J4R::Reader.new('test.xml', :marcxml)
  
    # Or use a file object
  
    reader = MARC4J4R::Reader.new(File.open('test.mrc'))
    
    # Or a java.io.inputstream
  
    jurl = Java::java.net.URL.new('http://my.machine.com/test.mrc')
    istream = jurl.openConnection.getInputStream
    reader = MARC4J4R::Reader.new(istream)

## Using the reader

A MARC4J4R::Reader is an Enumerable, so you can do:

    reader.each do |record|
      # do stuff with the record
    end

Or, if you're using [threach](http://rdoc.info/projects/billdueber/threach):

    reader.threach(2) do |record|
      # do stuff with records in two threads
    end
  
## Using the writer

The writer code has not yet been tested; it *should* work as follows:

      binaryWriter = MARC4J4R::Writer.new(filename, :strictmarc)
      xmlWriter    = MARC4J4R::Writer.new(filename, :marcxml)
  
      writer.write(record)
      # repeat
      writer.close


## Working with records and fields

In addition to all the normal marc4j methods, MARC4J4R::Record exposes some additional methods
and syntaxes. 

**See the classes themselves and/or the specs for more examples.**

     leader = record.leader

     # All fields are available via #each or #fields
   
     fields = record.fields

     record.each do |field|
       # do something with each controlfield/datafield; returned in the order they were added
     end
   
     # Controlfields have a tag and a value

     idfield = record['001']
     idfield.tag # => '001'
     id = idfield.value # or idfield.data, same thing
   
     # Get the first datafield with a given tag
     first700 = record['700'] # Note: need to use strings, not integers
   
     # Stringify a field to get all the subfields joined with spaces
   
     fullTitle = record['245'].to_s
   
     all700s  = record.find_by_tag '700'
     all700and856s = record.find_by_tag ['700', '856']

   
     # Construct and add a controlfield
     record << MARC4J4R::ControlField.new('001', '0000333234')
   
     # Construct and add a datafield
     df = MARC4J4R::DataField.new(tag, ind1, ind2)
   
     ind1 = df.ind1
     ind2 = df.ind2
   
     df << MARC4J4R::Subfield.new('a', 'the $a value')
     df << MARC4J4R::Subfield.new('b', 'the $b value')   
   
     # Add it to a record
   
     record << df
   
     # Get subfields or their values
   
     firstSubfieldAValue = df['a']
   
     allSubfields = df.subs
     allSubfieldAs = df.subs('a')
     allSubfieldAorBs = df.subs(['a', 'b'])
   
     allSubfieldAorBValues = df.sub_values(['a', 'b'])


## Note on Patches/Pull Requests
 
* Fork the project.
* Make your feature addition or bug fix.
* Add tests for it. This is important so I don't break it in a
  future version unintentionally.
* Commit, do not mess with rakefile, version, or history.
  (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
* Send me a pull request. Bonus points for topic branches.

## Copyright

Copyright (c) 2010 BillDueber. See LICENSE for details.