Ruby Forum Ruby on Rails > Need Explainantion of ActiveRecord::Base.transaction

Dear All:

Any one can help me to explain what is it for:

[1] ActiveRecord::Base.transaction and Customer.transaction ?

[2] What is deferences ActiveRecord::Base.transaction and
Customer.transaction ?

[3] Is it the same like Transaction Support?

[4] Any one can give me proof of concept of
ActiveRecord::Base.transaction ?

Thank you very much for your time and help.


Best Regards,
Reinhart

On 7 May 2008, at 03:28, Rails Terrorist wrote:

>
> Dear All:
>
> Any one can help me to explain what is it for:
>
> [1] ActiveRecord::Base.transaction and Customer.transaction ?
Most of the time they are identical. They're different if
Customer.connection != ActiveRecord::Base.connection

> [2] What is deferences ActiveRecord::Base.transaction and
> Customer.transaction ?
No idea what you are talking about
> [3] Is it the same like Transaction Support?
>
they are for database transactions
> [4] Any one can give me proof of concept of
> ActiveRecord::Base.transaction ?
>
Customer.transaction do
   #do something
end

Fred

Thank You Fred,

I need to know :

[1] When do I use Model_name.transaction and When do I use 
ActiveRecord::Base.transaction?

[2] I have related tables in database and they are depended one each 
other. And they need having transaction support in a method. Which is 
good ActiveRecord::Base.transaction or each name_model.transaction ?

[3] Any good reference article that can explain it detail? I cant get it 
in google. Only sample code, but not explain process in transaction.


Once Again, Thank you very much.

Reinhart

On 7 May 2008, at 11:23, Rails Terrorist wrote:

> good ActiveRecord::Base.transaction or each name_model.transaction ?
>
>
Unless you're playing with multiple databases they're all the same

> [3] Any good reference article that can explain it detail? I cant  
> get it
> in google. Only sample code, but not explain process in transaction.

Don't know about that. there's not really an awful lot to say, it's
just a means of running some code inside a database transaction. If an
exception is thrown it's rolled back, if not it's committed  (there's
a specific exception you can throw to just roll back, can't remember
the name but it will be in the docs.

Fred

Unless you do something specific to override the default
functionality, a model that inherits from ActiveRecord::Base inherits
the db connection that it uses.  Indirectly, this means that ALL the
models that inherit from ARec::Base will use the same connection
(again, barring a specific override).

The transaction method, as Fred explains, provides an explicit way to
mark the beginning and end of a db transaction.  The transaction is
run in the context of the db connection.  If you have not done
anything to override the way that your model sets/gets its DB
connection then there is absolutely no difference between using
transaction on ARec::Base or any of the models that inherited from it.

On May 7, 7:02 am, Frederick Cheung <frederick.che...@gmail.com>

Thanks guys, I understand. But example if i have more than 1 models for 
transaction, could i use ActiveRecord::Base.transaction like sample 
below:

ActiveRecord::Base.transaction do

  @lecturer_A = AlphaDepartment.new(params[:alpha_lecturer])

    if @lecturer_A.save
       @lecturer_A_in_B = BetaDepartment.find_by_ssn(@lecturer_A.ssn)
       @lecturer_A_in_D = DeltaDepartment.find_by_ssn(@lecturer_A.ssn)

       if @lecturer_A_in_B.start_work < 5.years
          @lecturer_A_in_B.histories.delete_all
          @lecturer_A_in_B.histories << @lecturer_A_in_D.histories
       else
          @lecturer_A.histories << @lecturer_A_in_B.histories
       end
    end
end

What should I use AlphaDepartment.transaction, 
BetaDepartment.transaction & DeltaDepartment.transaction together in 1 
action like above? any suggestion?


Thank You,
Reinhart