help updating cross-reference table

rubyonrails-talk
1

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?

2

Quoting Mr. Bill <rails-mailing-list@andreas-s.net>:

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

3

Quoting Jeffrey L. Taylor <ror@austinblues.dyndns.org>:

Quoting Mr. Bill <rails-mailing-list@andreas-s.net>: > > 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

4

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:

5

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