Help updating cross-reference table

Rails
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 Jeffrey L. Taylor [email protected]:

  @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

3

Quoting Mr. Bill [email protected]:

  @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

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:

Quoting Jeffrey L. Taylor [email protected]:

  @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

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