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Mr. Bill

2008-Jan-06 22:36 UTC

help updating cross-reference table

I am trying to update a cross-reference table in a database when the
user submits a simple form. The table has three columns, ''id'',
''location_id'' and ''user_id''.

Using this action, I get no errors, but nothing happens to the table:

    def update
      @user = User.find(params[:id])
      @locations = Location.find(:all)
      @locationsusers = LocationsUser.find(params[:id])
      if @locationsusers.update_attributes(:user_id => @user,
:location_id => @locations)
        flash[:notice] = ''Data was successfully updated.''
        redirect_to :action => ''list''
      else
        render :action => ''edit''
      end
    end

If I try to substitute the update_attributes line with:

   if @locationsusers.update_attributes(params[:id])

I see the error,
"undefined method `stringify_keys!'' for
"3":String".

If I try to do this:

   @locationsusers = LocationsUser.find(:all)
   if @locationsusers.update_attributes(params[:id])

I see the error,
"NoMethodError in UserController#updateLocation
undefined method `update_attributes''"

How can I do this correctly?
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Jeffrey L. Taylor

2008-Jan-07 10:01 UTC

head link

Re: help updating cross-reference table

Quoting Mr. Bill
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:> 
> I am trying to update a cross-reference table in a database when the
> user submits a simple form. The table has three columns,
''id'',
> ''location_id'' and ''user_id''.
> 
> Using this action, I get no errors, but nothing happens to the table:
> 
>     def update
>       @user = User.find(params[:id])
>       @locations = Location.find(:all)
>       @locationsusers = LocationsUser.find(params[:id])
>       if @locationsusers.update_attributes(:user_id => @user,
> :location_id => @locations)
Try:
  if @locationusers.update_attributes(:user_id => @user.id,

However, since @locations is an array of Location(s), this code probably
isn''t
what you want at all.  You could do:

  if @locationusers.update_attributes(:user_id => @user.id,
     :location_id => @locations.map(&:id)

But what you probably want is a :has_many :through association table.  Off the
top of my head:

Class LocationUsers < ActiveRecord::Base
  belongs_to :user
  belongs_to :location
end

Class Users < ActiveRecord::Base
  has_many :location_users
  has_many :locations, :through => :location_users
end

Class Locations < ActiveRecord::Base
  has_many :location_users
  has_many :users, :through => :location_users
end


def update
  @user = User.find(params[:id])
  @locations = Location.find(:all)
  @locations.each {|l| @user.locations << l}
end


HTH,
  Jeffrey

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Jeffrey L. Taylor

2008-Jan-07 14:29 UTC

head link

Re: help updating cross-reference table

Quoting Jeffrey L. Taylor
<ror-NvlhjL+mh2pvqUDvg8NhqHL8HoS0Hn3T@public.gmane.org>:> 
> Quoting Mr. Bill
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
> > 
> > I am trying to update a cross-reference table in a database when the
> > user submits a simple form. The table has three columns,
''id'',
> > ''location_id'' and ''user_id''.
> > 
> > Using this action, I get no errors, but nothing happens to the table:
> > 
> >     def update
> >       @user = User.find(params[:id])
> >       @locations = Location.find(:all)
> >       @locationsusers = LocationsUser.find(params[:id])
> >       if @locationsusers.update_attributes(:user_id => @user,
> > :location_id => @locations)
> 
> Try:
>   if @locationusers.update_attributes(:user_id => @user.id,
> 
> However, since @locations is an array of Location(s), this code probably
isn''t
> what you want at all.  You could do:
> 
>   if @locationusers.update_attributes(:user_id => @user.id,
>      :location_id => @locations.map(&:id)
> 
> But what you probably want is a :has_many :through association table.  Off
the
> top of my head:
> [snip]
If there will never be any values in the cross-reference (AKA join) table,
i.e., just the three columns mentioned, the conceptually simpler
has_and_belongs_to_many relationship works.  IIRC, the join table should be
named LocationsUsers.  There is a way to override the join table name, perhaps
through:

Class User < ActiveRecord::Base
  has_and_belongs_to_many :locations, :through => :location_users
end

Class Location < ActiveRecord::Base
  has_many :location_users
  has_many :users, :through => :location_users
end


The update code is the same.  Oh, and the class names in the previous example
should be singular.

HTH,
  Jeffrey

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Mr. Bill

2008-Jan-07 15:45 UTC

head link

Re: help updating cross-reference table

Thank you for your assistance Jeffrey. Your comments have helped.

When I try to do:
def update
  @user = User.find(params[:id])
  @locations = Location.find(:all)
  @locations.each {|l| @user.locations << l}
end

I see this error:
"TypeError in UserController#updateLocation
can''t convert Location into Integer"


When I do:
@locationsusers = LocationsUser.find(params[:id])
if @locationsusers.update_attributes(:user_id => @user.id, :location_id 
=> @locations.map(&:id))

I don''t see any errors, but nothing changes in the database table.
Is there something else I''m missing?


Jeffrey L. Taylor wrote:> Quoting Jeffrey L. Taylor
<ror-NvlhjL+mh2pvqUDvg8NhqHL8HoS0Hn3T@public.gmane.org>:
>> >       @user = User.find(params[:id])
>> 
>>   if @locationusers.update_attributes(:user_id => @user.id,
>>      :location_id => @locations.map(&:id)
>> 
>> But what you probably want is a :has_many :through association table. 
Off the
>> top of my head:
>> 
> [snip]
> If there will never be any values in the cross-reference (AKA join) 
> table,
> i.e., just the three columns mentioned, the conceptually simpler
> has_and_belongs_to_many relationship works.  IIRC, the join table should 
> be
> named LocationsUsers.  There is a way to override the join table name, 
> perhaps
> through:
> 
> Class User < ActiveRecord::Base
>   has_and_belongs_to_many :locations, :through => :location_users
> end
> 
> Class Location < ActiveRecord::Base
>   has_many :location_users
>   has_many :users, :through => :location_users
> end
> 
> 
> The update code is the same.  Oh, and the class names in the previous 
> example
> should be singular.
> 
> HTH,
>   Jeffrey
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Mr. Bill

2008-Jan-07 18:23 UTC

head link

Re: help updating cross-reference table

Eureka! The action below did the trick.
Thank you for all your help Jeffrey. The suggestions on the models 
worked also.

def update
    @user = User.find(params[:id])
    @locations = Location.find(:all)
    @locations.each do |location|
      @locationsids = location.id
    end
    @locationsusers = LocationsUser.new
    @locationsusers.user_id = @user.id
    @locationsusers.location_id = @locationsids.id
    if @locationsusers.update_attributes(params[:locations_users])
      flash[:notice] = ''User was successfully updated.''
      redirect_to :action => ''list''
    else
      render :action => ''edit''
    end
end

-- 
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Rails - Jan 2008 - help updating cross-reference table

help updating cross-reference table

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