obo_parser

gem install obo_parser

require 'obo_parser'
o = parse_obo_file(File.read('my_ontology.obo'))  # => An OboParser instance  
first_term = o.terms.first                        # => An OboParser#Term instance 

first_term.id.value                                 # => 'HAO:1234'

d = first_term.def                                  # => An OboParser#Tag instance
d.tag                                               # => 'def'
d.value                                             # => 'Some defintition'
d.xrefs                                             # => ['xref:123', 'xref:456'] 
d.comment                                           # => 'Some comment'

t = first_term.name                                 # => An OboParser#Tag instance    
t.tag                                               # => 'name'
t.value                                             # => 'Some Term name' 

o = first_term.other_tags                           # => [OboParser#Tag, ... ] An array of tags that are not specially referenced in an OboParser::Stanza
o.first                                             # => An OboParser#Tag instance    

first_typedef = o.typdefs.first                   # => An OboParser#Typdef instance 
first_typdef.id.value                               # => 'Some typedef id'
first_typdef.name.value                             # => 'Some typedef name'

o.terms.first.tags_named('synonym')               # => [OboParser#Tag, ... ]
o.terms.first.tags_named('synonym').first.tag     # => 'synonym'
o.terms.first.tags_named('synonym').first.value   # => 'Some label'

o.terms.first.relationships                       # => [['relationship', 'FOO:123'], ['other_relationship', 'FOO:456'] ...] An array of [relation, related term id], includes 'is_a', 'disjoint_from' and Typedefs

o.term_hash                                       # => { term (String) => id (String), ... for each [Term] in the file. } !! Assumes names terms are unique, they might not be, in which case you get key collisions. 
o.id_hash                                         # => { id (String) => term (String), ... for each [Term] in the file. } 

OboParser::Utilities::Viz.mock_coordinate_space(o, size: 100) # => STDOUT tab delimited table with x, y, z, identifier, label