Hello,
I am new to RoR and am coding a small budgetting app with two tables
(see below). As you can see every account has_many transactions and
every transaction has 2 accounts. How can I best respresent this using
ActiveRecord::Associations ?
create table accounts (
id int not null auto_increment,
name varchar(100) not null default '''',
primary key(id)
);
create table transactions (
id int not null
auto_increment,
month varchar(3) not null,
amount int null,
from_id int not null,
to_id int not null,
constraint fk_from_accounts foreign key (from_id) references
accounts(id),
constraint fk_to_accounts foreign key (to_id) references
accounts(id),
primary key(id)
) engine=InnoDB;
I see 3 possible solutions but nothing elegant:
- create 2 relationship tables (from and to)
- use sql
- code belongs_to_2 association
I would very much like your advice on this.
Thanks !
Simon
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Steve Tooke
2007-Jun-29 16:12 UTC
Re: How to handle cardinality 1-to-2 with Associations ?
Hi Simon, I think you need to model two relationships. class Transaction < AR::Base belongs_to :creditor, :class_name => ''Account'', :foreign_key => ''creditor_id'' #from_id belongs_to :debitor, :class_name => ''Account'', :foreign_key => ''debitor_id'' #to_id end class Account < AR:Base has_many :credits, :class_name => ''Transaction'', :foreign_key => ''creditor_id'' #from_id has_many :debits, : class_name => ''Transaction'', :foreign_key => ''debitor_id'' #to_id end Steve On Jun 29, 4:51 pm, Simon <geza.hercz...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> Hello, > > I am new to RoR and am coding a small budgetting app with two tables > (see below). As you can see every account has_many transactions and > every transaction has 2 accounts. How can I best respresent this using > ActiveRecord::Associations ? > > create table accounts ( > id int not null auto_increment, > name varchar(100) not null default '''', > primary key(id) > ); > > create table transactions ( > id int not null > auto_increment, > month varchar(3) not null, > amount int null, > from_id int not null, > to_id int not null, > constraint fk_from_accounts foreign key (from_id) references > accounts(id), > constraint fk_to_accounts foreign key (to_id) references > accounts(id), > primary key(id) > ) engine=InnoDB; > > I see 3 possible solutions but nothing elegant: > - create 2 relationship tables (from and to) > - use sql > - code belongs_to_2 association > > I would very much like your advice on this. > > Thanks ! > Simon--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Michael Latta
2007-Jun-29 18:21 UTC
Re: How to handle cardinality 1-to-2 with Associations ?
That certainly works. You can also put in a validation for the transaction and the account classes to limit the number of associations between them if you want to treat all associations uniformly. Michael On Jun 29, 2007, at 9:12 AM, Steve Tooke wrote:> > Hi Simon, > > I think you need to model two relationships. > > class Transaction < AR::Base > belongs_to :creditor, :class_name => ''Account'', :foreign_key => > ''creditor_id'' #from_id > belongs_to :debitor, :class_name => ''Account'', :foreign_key => > ''debitor_id'' #to_id > end > > class Account < AR:Base > has_many :credits, :class_name => ''Transaction'', :foreign_key => > ''creditor_id'' #from_id > has_many :debits, : class_name => ''Transaction'', :foreign_key => > ''debitor_id'' #to_id > end > > Steve > > On Jun 29, 4:51 pm, Simon <geza.hercz...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: >> Hello, >> >> I am new to RoR and am coding a small budgetting app with two tables >> (see below). As you can see every account has_many transactions and >> every transaction has 2 accounts. How can I best respresent this >> using >> ActiveRecord::Associations ? >> >> create table accounts ( >> id int not null auto_increment, >> name varchar(100) not null default '''', >> primary key(id) >> ); >> >> create table transactions ( >> id int not null >> auto_increment, >> month varchar(3) not null, >> amount int null, >> from_id int not null, >> to_id int not null, >> constraint fk_from_accounts foreign key (from_id) references >> accounts(id), >> constraint fk_to_accounts foreign key (to_id) references >> accounts(id), >> primary key(id) >> ) engine=InnoDB; >> >> I see 3 possible solutions but nothing elegant: >> - create 2 relationship tables (from and to) >> - use sql >> - code belongs_to_2 association >> >> I would very much like your advice on this. >> >> Thanks ! >> Simon > > > --~--~---------~--~----~------------~-------~--~----~ > You received this message because you are subscribed to the Google > Groups "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org > To unsubscribe from this group, send email to rubyonrails-talk- > unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org > For more options, visit this group at http://groups.google.com/ > group/rubyonrails-talk?hl=en > -~----------~----~----~----~------~----~------~--~--- >
Thanks you Steve, that is exactly what I was looking for. (I got so close but couldn''t figure it out :-) ). Simon On Jun 29, 6:12 pm, Steve Tooke <steve.to...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> Hi Simon, > > I think you need to model two relationships. > > class Transaction < AR::Base > belongs_to :creditor, :class_name => ''Account'', :foreign_key => > ''creditor_id'' #from_id > belongs_to :debitor, :class_name => ''Account'', :foreign_key => > ''debitor_id'' #to_id > end > > class Account < AR:Base > has_many :credits, :class_name => ''Transaction'', :foreign_key => > ''creditor_id'' #from_id > has_many :debits, : class_name => ''Transaction'', :foreign_key => > ''debitor_id'' #to_id > end > > Steve > > On Jun 29, 4:51 pm, Simon <geza.hercz...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > > > Hello, > > > I am new to RoR and am coding a small budgetting app with two tables > > (see below). As you can see every account has_many transactions and > > every transaction has 2 accounts. How can I best respresent this using > > ActiveRecord::Associations ? > > > create table accounts ( > > id int not null auto_increment, > > name varchar(100) not null default '''', > > primary key(id) > > ); > > > create table transactions ( > > id int not null > > auto_increment, > > month varchar(3) not null, > > amount int null, > > from_id int not null, > > to_id int not null, > > constraint fk_from_accounts foreign key (from_id) references > > accounts(id), > > constraint fk_to_accounts foreign key (to_id) references > > accounts(id), > > primary key(id) > > ) engine=InnoDB; > > > I see 3 possible solutions but nothing elegant: > > - create 2 relationship tables (from and to) > > - use sql > > - code belongs_to_2 association > > > I would very much like your advice on this. > > > Thanks ! > > Simon--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---