Understanding this model relationship (possibly a HABTM and a belongs_to ?)

Rails
1

I’m pretty newb and trying to get a handle on setting up a particular
relationship with my models.

For sake of this discussion (real app isn’t with tools but for
illustration,
using tools):

To start with (more complicated in a bit);

  • A User can have multiple tools
  • A single tool can only belong to one ToolGroup
  • A User can belong to multiple ToolGroups

To model this relationship, I was thinking:

User
has_many :tools
has_and_belong_to_many :tool_groups

Tool
has_one :tool_group
belongs_to :user

ToolGroup
has_and_belongs_to_many :users

So first question, is the above set up correctly?

Once the above is set up correctly, I want to have it set up where a
ToolGroup can also be ‘owned’ by a User. In other words, a user will set
up
a ToolGroup and they are the owner, but other users can belong to this
ToolGroup. How do I model that? Do I need to set up another model that
is
called “Owner” that is really a “User”? This doesn’t seem right. In
reality
the db table “ToolGroup” would just need an “ownerID” that would be a fk
to
the User table, but I’m not sure how to model that since ToolGroup
already
has a HABTM to users. Can I have a HABTM to Users and also a belongs_to
:User?

Thanks for any help

2

My initial example is probably confusing. Here is another shot at it in
something that has more meaning:

A User can create multiple “notices” ( eg “Corporate meeting notice”,
“Big
Sale Items”, “Job Wanted” )
A User can create multiple “notice groups” (eg “Corporate Notices”,
“Public
Notices”, “My Miscellaneous Notices”)
Every notice should belong to an “notice group”
A User needs to be able to subscribe to multiple “notice groups” so that
they could see the notices in the different groups they’re subscribed
to.

To model this relationship, I was thinking:

User
has_many :notices
has_and_belong_to_many :notice_groups

Notice
has_one :notice_group
belongs_to :user

NoticeGroup
has_and_belongs_to_many :users

So first question, is the above set up correctly?

How would I also model that a “NoticeGroup” is ‘owned/created’ by a
particular user? Right now the HABTM on NoticeGroup seems to imply that
the
NoticeGroup can belong to many Users but I also need it to show that its
owned/created by a particular User (owner_id concept on NoticeGroup?),
can I
have a HABTM :users and a belongs_to :User in the same NoticeGroup model
definition?

On Wed, Aug 11, 2010 at 12:20 AM, Rick R [email protected] wrote:

  • A User can belong to multiple ToolGroups

called “Owner” that is really a “User”? This doesn’t seem right. In reality
the db table “ToolGroup” would just need an “ownerID” that would be a fk to
the User table, but I’m not sure how to model that since ToolGroup already
has a HABTM to users. Can I have a HABTM to Users and also a belongs_to
:User?

Thanks for any help

–
Rick R

3

Rick R wrote:

My initial example is probably confusing. Here is another shot at it in
something that has more meaning:

A User can create multiple “notices” ( eg “Corporate meeting notice”,
“Big
Sale Items”, “Job Wanted” )
A User can create multiple “notice groups” (eg “Corporate Notices”,
“Public
Notices”, “My Miscellaneous Notices”)

Are these notice groups specific to the one user, or are they more like
global discussion topics?

Can notice groups contain notices created by users other than the one
who created the group?

Every notice should belong to an “notice group”
A User needs to be able to subscribe to multiple “notice groups” so that
they could see the notices in the different groups they’re subscribed
to.

To model this relationship, I was thinking:

User
has_many :notices
has_and_belong_to_many :notice_groups

Notice
has_one :notice_group

That should be belongs_to, not has_one.

belongs_to :user

NoticeGroup
has_and_belongs_to_many :users

So first question, is the above set up correctly?

Maybe, maybe not. Depends on the questions above.

How would I also model that a “NoticeGroup” is ‘owned/created’ by a
particular user? Right now the HABTM on NoticeGroup seems to imply that
the
NoticeGroup can belong to many Users but I also need it to show that its
owned/created by a particular User (owner_id concept on NoticeGroup?),
can I
have a HABTM :users and a belongs_to :User in the same NoticeGroup model
definition?

Sure. Just give the associations different names.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

4

On Wed, Aug 11, 2010 at 2:26 PM, Marnen Laibow-Koser
[email protected]wrote:

Are these notice groups specific to the one user, or are they more like
global discussion topics?

They are “created by one user” but multiple users can subscribe to them:

“A User needs to be able to subscribe to multiple “notice groups” so
that
they could see the notices in the different groups they’re subscribed
to.”

Can notice groups contain notices created by users other than the one
who created the group?

No.

Sure. Just give the associations different names.

Ok, I’ll look into that. thanks.