Rails - Nov 2004 - RE: question about rails regarding handling more than onetable in one view

Hi, Jarkko:

 

Thanks for the quick reply. 

I understand I can use ActiveRecord to specify the relation between the
table as you have suggested,

The part that I have trouble to understand is

 

1. Since I have a third table ProvWorkAtDept, do I need to specify this
table somewhere when I define Provider or Dept?

2. If the provider view has both the provider name and several depts the
provider works on, how that data will be handled by the Provider model
or controller,

Do I need write code in Provider model (or the controller) to call
Provider#Dept<<Dept (or Provider#Dept.Build, Create) to save the
relation to ProvWorkAtDept table Or rails will handle it automatically?

 

It will be great if you give me some explanation between provider view,
model and the controller regarding how the depts will be filed.

 

Thanks again

chong

 

 

 

 

________________________________

From: rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
[mailto:rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org] On
Behalf Of Jarkko Laine
Sent: Tuesday, November 30, 2004 10:42 AM
To: rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
Subject: Re: [Rails] question about rails regarding handling more than
onetable in one view

 

Hi Chong, 

 

Rails has indeed magic to take care of both one-to-many and many-to-many
relationships. Please read
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethod
s.html which has an extensive explanation of how associations work in
Rails. 

 

For your example: 

 

class Provider > ActiveRecord::Base 

has_and_belongs_to_many :depts 

end 

 

class Dept > ActiveRecord::Base 

has_and_belongs_to_many :providers 

end 

 

class Order > ActiveRecord::Base 

has_many :orderitems 

end 

 

class Orderitem > ActiveRecord::Base 

belongs_to :order 

end 

 

HTH, 

Jarkko 

 

On 30.11.2004, at 18:16, ChongQing Xiao wrote: 

	 

	Hi, Everyone 

	 

	I am just starting to look at the rail and really like how it
works. 

	 

	One question I can not figure out is how rails will solve the
following problem. 

	 

	I have 3 tables 

	 

	Table 1 - Provider table 

	 

	ProvID 

	 

	Name 

	 

	Table 2 - Dept Table 

	 

	DeptId 

	 

	Name 

	 

	Table 3 - ProvWorkAtDept 

	 

	ProvID   

	 

	DeptID 

	 

	Table 3 is the relation table between provider and dept and one
provider can work at more than one dept. 

	 

	Now if I want to have a view for provider which will let the
user edit specific provider 

	 

	-       name 

	 

	-       dept lists (the user can enters multi dept for this
particular provider) 

	 

	If I have a provider model, how the model will handle the dept
lists since the dept lists is in a separate table, do I need to write 

	 

	Code to handle it or rails have some magic way to handle this
problem. 

	 

	Also, How rails will handle master detail relation which is
common in database application (such as order and order items)? 

	 

	Thanks a lot 

	 

	chong 

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-- 

Jarkko Laine 

http://jlaine.net 



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Hi Chong,

On 30.11.2004, at 19:07, ChongQing Xiao wrote:
>
> 1. Since I have a third table ProvWorkAtDept, do I need to specify  
> this table somewhere when I define Provider or Dept?
 From  
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ 
ClassMethods.html#M000121:

has_and_belongs_to_many
Associates two classes via an intermediate join table. Unless the join  
table is explicitly specified as an option, it is guessed using the  
lexical order of the class names. So a join between Developer and  
Project will give the default join table name of "developers_projects"
because "D" outranks "P".
>
> 2. If the provider view has both the provider name and several depts  
> the provider works on, how that data will be handled by the Provider  
> model or controller,
You will have a method called Provider#depts which will return an array  
(I think) consisting of Dept objects. Plus many other nifty methods  
that you can find from that same address above.
>
> Do I need write code in Provider model (or the controller) to call  
> Provider#Dept<<Dept (or Provider#Dept.Build, Create) to save the  
> relation to ProvWorkAtDept table Or rails will handle it  
> automatically?
Provider#depts<< @deptobject

will do what is needed. You don''t have to write any additional code.
> It will be great if you give me some explanation between provider  
> view, model and the controller regarding how the depts will be filed.
This all has been part of ActiveRecord (=model). You will of course  
call those functions (like Provider#depts<< @deptobject) in your  
controllers.

Hope this made things a bit clearer.

//jarkko
--
Jarkko Laine
http://jlaine.net



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