From: Peñá, Botp [mailto:botp / delmonte-phil.com] 
# >> people_array.map{ |p| p.name }
# => ["bob", "dave", "jane"]

pls ignore above, i'm still searching my lost brain :)

try #group_by,

> people_array.group_by{ |p| p.name }
=> {"bob"=>[#<struct Person name="bob", age=12, city="SFO">], "dave"=>[#<struct Person name="dave", age=14, city="NYC">], "jane"=>[#<struct Person name="jane", age=6, city="LDN">]}