has_and_belongs_to_many migration problem i am facing

[Fahim Patel]

I have two models cow and milkman.

I am using has_and_belongs_to_many in both models .

By mistake i have deleted cows_milkmans table from database.

When i use  this command i am getting error

a = Cow.last

a.milkmans  #  when i fire this command then i am getting error that cows_milkmans table not exist

As per my knowledge has_and_belongs_to_many will create third table automatically , no migration is needed.

How can get that table ?

[vijaya sekhar reddy mallidi]

Hi pafahim,

   When you use HABM association in your models It will not generate the join table automatically. We have to create manually.

  For your issue try to rollback the join table from database.

Thanks & Regards,

  VIjay

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[Fahim Patel]

No man ...

i just use HABM in models and when i fire command in  console at that point   third table is created.

And i do nothing manually..

[Jim Ruther Nill]

On Fri, Sep 21, 2012 at 9:07 PM, Fahim Patel <paf...@gmail.com> wrote:

No man ...

i just use HABM in models and when i fire command in  console at that point   third table is created.

And i do nothing manually..

Hi!

I don't use habtm so I'm not familiar with how it work in core.  But reading from http://guides.rubyonrails.org/association_basics.html#the-has_and_belongs_to_many-association

The simplest rule of thumb is that you should set up a has_many :through relationship if you need to work with the relationship model as an independent entity. If you don’t need to do anything with the relationship model, it may be simpler to set up a has_and_belongs_to_many relationship (though you’ll need to remember to create the joining table in the database).

You should use has_many :through if you need validations, callbacks, or extra attributes on the join model.

So I guess you need to create that table in the database manually.

 

On Friday, September 21, 2012 3:51:41 PM UTC+5:30, Fahim Patel wrote:

I have two models cow and milkman.

I am using has_and_belongs_to_many in both models .

By mistake i have deleted cows_milkmans table from database.

When i use  this command i am getting error

a = Cow.last

a.milkmans  #  when i fire this command then i am getting error that cows_milkmans table not exist

As per my knowledge has_and_belongs_to_many will create third table automatically , no migration is needed.

How can get that table ?

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[Dave Aronson]

On Sat, Sep 22, 2012 at 6:00 AM, Jim Ruther Nill <jvn...@gmail.com> wrote:

> reading from
> http://guides.rubyonrails.org/association_basics.html#the-has_and_belongs_to_many-association
>
> The simplest rule of thumb is that you should set up a has_many :through
> relationship if you need to work with the relationship model as an
> independent entity. If you don’t need to do anything with the relationship
> model, it may be simpler to set up a has_and_belongs_to_many relationship
> (though you’ll need to remember to create the joining table in the
> database).
>
> You should use has_many :through if you need validations, callbacks, or
> extra attributes on the join model.

Also, I haven't had to do it myself, but I've heard that retrofitting
a habtm setup to use hmt, after discovering a need for any of the
above, can be a royal pain in the proverbial posterior. So, I usually
just ignore habtm, and use hmt for all such joins.

-Dave

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