Formatting data before ActiveRecord insertion

Rails
1

Hello,

Sorry if this is a noob question.

I’m trying to store a hash of values (a user’s music collection) into a
single database record without having to have a separate row in the db
for
each music track the user has in his collection.

e.g. User 9
{ 12319 => “Artist X: Song Name 1”,
12198 => “Artist X: Song Name 2”,
19180 => “Artist Y: Song Name 3”,
92810 => “Artist Z: Song Name 4” }

I’m going serialize this hash with serialize: and store it in a text
field.

I’d like the create, update_attributes, save, etc. methods that could
potentially write to this field to create this hash structure (if none
exists), add to the hash structure, or remove an entity from this
structure
automatically without someone using my model having to manually getting
the
record, read the hash and adding/deleting from the hash.

I’ve thought about the following as options:

  1. attr_protected :music_tracks
    and write a custom accessor to manipulate the hash.

  2. overriding the create, update_attributes, save etc. methods of
    ActiveRecord to manipulate the hash.

Am I going about this wrong, or any suggestions on the 2 options?

Thanks,
Tom

2

On 5 September 2010 00:31, Tom F. [email protected]
wrote:

Hello,
Sorry if this is a noob question.
I’m trying to store a hash of values (a user’s music collection) into a
single database record without having to have a separate row in the db for
each music track the user has in his collection.
e.g. User 9
{ 12319 => “Artist X: Song Name 1”,
12198 => “Artist X: Song Name 2”,
19180 => “Artist Y: Song Name 3”,
92810 => “Artist Z: Song Name 4” }

Not answering the question, I know, but I would advise against doing
it this way. Have a tracks table, User has_many tracks, Track
belongs_to user. Then for a user his tracks are
current_user.tracks
and for each track the artist and name are track.artist and track.name.
You will not have to write all the code you are struggling with, Rails
will do it for you. The less code you have to write the better.

Colin

3

You can manipulate data before saving it

class User
before_save :do_something

def do_something
// process music_tracks here
end
end

PS: I do not know the purpose of your project, but in general, having
a table of songs referred by id seems a better option to me.

Song 1 => { band => “Kiss”, “title” => “Strutter” }
User 1 => [1, 1, 1]
User 2 => [1, 1, 1]
User 3 => [1, 1, 1]

In your case, you will get multiple copies of bloated data spread all
over DB if many users listen to the same song over and over again.

User 1 => { 1 => “Kiss: Strutter”,
2 => “Kiss: Strutter”,
3 => “Kiss: Strutter” }
User 2 => { 1 => “Kiss: Strutter”,
2 => “Kiss: Strutter”,
3 => “Kiss: Strutter” }
User 3 => { 1 => “Kiss: Strutter”,
2 => “Kiss: Strutter”,
3 => “Kiss: Strutter” }