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Felipe Pieretti Umpierre

2012-Feb-14 01:43 UTC

What I''m doing wrong, has_and_belong_to_many

Hello, I''m trying to insert into my migrate but when I try on rails
console this error shows:

1.9.3-p0 :001 > group = Group.new
 => #<Group id: nil, name: nil, description: nil, created_at: nil,
updated_at: nil>
1.9.3-p0 :002 > group.name = "Group Name"
 => "Group Name"
1.9.3-p0 :003 > group.description = "Description"
 => "Description"
1.9.3-p0 :004 > group.save
   (0.2ms)  BEGIN
  SQL (0.4ms)  INSERT INTO `groups` (`created_at`, `description`,
`name`, `updated_at`) VALUES (''2012-02-14 01:39:22'',
''Description'',
''Group Name'', ''2012-02-14 01:39:22'')
   (124.5ms)  COMMIT
 => true
1.9.3-p0 :005 > email = Email.new
 => #<Email id: nil, name: nil, email: nil, sex: "M",
created_at: nil,
updated_at: nil>
1.9.3-p0 :006 > email.name = "Gremio10"
 => "Gremio10"
1.9.3-p0 :007 > email.email = "gremio-kBReAod5fl8@public.gmane.org"
 => "gremio-kBReAod5fl8@public.gmane.org"
1.9.3-p0 :008 > email.save
   (0.2ms)  BEGIN
  SQL (0.5ms)  INSERT INTO `emails` (`created_at`, `email`, `name`,
`sex`, `updated_at`) VALUES (''2012-02-14 01:39:56'',
''gremio-kBReAod5fl8@public.gmane.org'',
''Gremio10'', ''M'', ''2012-02-14
01:39:56'')
   (65.6ms)  COMMIT
 => true
1.9.3-p0 :009 > group << email
NoMethodError: undefined method `<<'' for #<Group:0xa7efb80>
  from
/home/felipe/.rvm/gems/ruby-1.9.3-p0/gems/activemodel-3.2.1/lib/active_model/attribute_methods.rb:407:in
`method_missing''
  from
/home/felipe/.rvm/gems/ruby-1.9.3-p0/gems/activerecord-3.2.1/lib/active_record/attribute_methods.rb:126:in
`method_missing''
  from (irb):9
  from
/home/felipe/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.1/lib/rails/commands/console.rb:47:in
`start''
  from
/home/felipe/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.1/lib/rails/commands/console.rb:8:in
`start''
  from
/home/felipe/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.1/lib/rails/commands.rb:41:in
`<top (required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3-p0 :010 >

My EmailModel

class Email < ActiveRecord::Base
  has_and_belongs_to_many :groups
  validate :email
end

My GroupModel

class Group < ActiveRecord::Base
  has_and_belongs_to_many :emails
  validate :name
end

My GroupsMigrate

class CreateGroups < ActiveRecord::Migration
  def change
    create_table :groups do |t|
      t.string "name"
      t.string "description"
      t.timestamps
    end
  end

  def down
    drop_table :groups
  end
end

My EmailsMigrate

class CreateEmails < ActiveRecord::Migration
  def change
    create_table :emails do |t|
      t.string "name"
      t.string "email"
      t.string "sex", :default => "M", :limit => 1
      t.timestamps
    end
  end

  def down
    drop_table :emails
  end
end

My EmailsGroupsMigrate

class CreateEmailsGroupsJoin < ActiveRecord::Migration
  def up
    create_table :emails_groups, :id => false do |t|
      t.references :email
      t.references :group
    end

    add_index :emails_groups, [ "email_id", "group_id" ]
  end

  def down
    drop_table :emails_groups
  end
end


Thank you.

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Dave Aronson

2012-Feb-14 02:23 UTC

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Re: What I''m doing wrong, has_and_belong_to_many

On Mon, Feb 13, 2012 at 20:43, Felipe Pieretti Umpierre
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
> Hello, I''m trying to insert into my migrate but when I try on
rails
> console this error shows:
...> 1.9.3-p0 :009 > group << email
> NoMethodError: undefined method `<<'' for
#<Group:0xa7efb80>
This is the chunk you need to worry about.  It''s telling you that you
haven''t defined any << method for your Group model.  AR
doesn''t
provide one, as such a thing just wouldn''t make sense for most models.
> class Email < ActiveRecord::Base
>  has_and_belongs_to_many :groups
>  validate :email
> end
...> class Group < ActiveRecord::Base
>  has_and_belongs_to_many :emails
>  validate :name
> end
You may also want to consider using "has_many :through" rather than
has_and_belongs_to_many.  I''ve heard horror stories of people having
trouble getting HABTM to work right (though I never had problems with
it myself), and if you ever decide you want to "decorate" that
relationship with any additional data, it can be very difficult to
retrofit a HABTM relationship to become HMT.

-Dave

-- 
Dave Aronson:  Available Cleared Ruby on Rails Freelancer
(NoVa/DC/Remote) -- see www.DaveAronson.com, and blogs at
www.Codosaur.us, www.Dare2XL.com, www.RecruitingRants.com

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Felipe Pieretti Umpierre

2012-Feb-14 11:47 UTC

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Re: What I''m doing wrong, has_and_belong_to_many

If I don''t have the method ''<<'', how can I
install on my rails ?

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thiagocifani

2012-Feb-14 12:06 UTC

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Re: Re: What I''m doing wrong, has_and_belong_to_many

If you have a has_many relationship or if you have any collection, you will
be able to use the append method << .

att

2012/2/14 Felipe Pieretti Umpierre
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
> If I don''t have the method ''<<'', how can I
install on my rails ?
>
> --
> Posted via http://www.ruby-forum.com/.
>
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> "Ruby on Rails: Talk" group.
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>
>

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Felipe Pieretti Umpierre

2012-Feb-15 01:54 UTC

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Re: What I''m doing wrong, has_and_belong_to_many

My error:

I was doing this -> group << email

But the correct is doing this -> group.emails << email

Thank you

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