[LRUG] Unexpected behaviour of << operator

[Marcus Roberts]

I've just been chasing down a weird bug, the cause of which was accidentally using << instead of =

But this led me to try and work out how an ActiveRecord object field was updating

A simple example:

>> p = Project.find 1
=> #<Project id: 1, user_id: 1, name: "A project name", ...>
>> n = p.name
=> "A project name"
>> n += "_extra"
=> "A project name_extra"
>> p.name
=> "A project name"

but 

>> p = Project.find 1
=> #<Project id: 1, user_id: 1, name: "A project name", ...>
>> n = p.name
=> "A project name"
>> n << "_extra"
=> "A project name_extra"
>> p.name
=> "A project name_extra"

I suspect this is something to do with clever overloading of <<  or my complete mis-understanding of something fundamental, but does anyone know why the change gets passed back through when I expected the original variable n to be a value, and not a reference

Marcus