gistfile1.txt

ree-1.8.7-2011.03 :001 > messages = []
 => [] 
ree-1.8.7-2011.03 :002 > messages << {:a => 1, :b => 2}
 => [{:b=>2, :a=>1}] 
ree-1.8.7-2011.03 :003 > messages << {:a => 3, :b => 4}
 => [{:b=>2, :a=>1}, {:b=>4, :a=>3}] 
ree-1.8.7-2011.03 :004 > messages.map do |m| 
ree-1.8.7-2011.03 :005 >     m[:a] = 5
ree-1.8.7-2011.03 :006?>   end
 => [5, 5] 
ree-1.8.7-2011.03 :007 > messages
 => [{:b=>2, :a=>5}, {:b=>4, :a=>5}] 
ree-1.8.7-2011.03 :008 > 


ree-1.8.7-2011.03 :012 > users = []
 => [] 
ree-1.8.7-2011.03 :013 > users << OpenStruct.new(:email => 'jack@gmail')
 => [#<OpenStruct email="jack@gmail">] 
ree-1.8.7-2011.03 :014 > users << OpenStruct.new(:email => 'nikhil@gmail')
 => [#<OpenStruct email="jack@gmail">, #<OpenStruct email="nikhil@gmail">] 
ree-1.8.7-2011.03 :015 > users.map do |user|
ree-1.8.7-2011.03 :016 >     user.email = 'newemail'
ree-1.8.7-2011.03 :017?>   end
 => ["newemail", "newemail"] 
ree-1.8.7-2011.03 :018 > users
 => [#<OpenStruct email="newemail">, #<OpenStruct email="newemail">] 
ree-1.8.7-2011.03 :019 >