Puzzled with form on multiple table rows

rubyonrails-talk
1

I've got a table of events, and each event has a boolean attribute is_ten_event.

On each row of the table is a chekbox to edit the value of is_ten_event, so that multiple rows can be edited with one submit.

In order to allow boxes to be un-checked as well, the logic in the controller works like this

get array of events from checkboxes that are ticked. make all events.is_ten_event = false make all events in array . is_ten_event = true

When I first check the checkbox and submit, everything works fine, the attribute is updated in the database and the table view reflects the changes. If I then submit again, with the same values still checked the values I set the last time get set to false.

The view code looks like this :

check_box_tag "is_ten_event_ids", event.id, event.is_ten_event

The controller is like this :

  def multi_params_edit

    @events = Event.find( params[:is_ten_event_ids] )     logger.debug("MULTI PARAMS EDIT : " + @events.length.to_s)

    unless @events.empty?

      Event.transaction do         Event.update_all(:is_ten_event => false)         @events.each do |e|           logger.debug("trying to make event is_ten_event = true")           e.update_attribute(:is_ten_event, true)         end       end     end

    redirect_to (:action =>:index)

  end

Here's the log output from the first submit (when it works)

Started POST "/admin/events/events/multi_params_edit" for 127.0.0.1 at Sun Aug 14 19:37:42 +0100 2011   Processing by Admin::Events::EventsController#multi_params_edit as HTML   Parameters: {"commit"=>"save changes (not functional)", "authenticity_token"=>"3MJ8aUhRWkrsOTLzkcLup8s7wrQH387H7uJeeKEU9Ss=", "utf8"=>"✓", "is_ten_event_ids"=>["5", "12", "20"]}   User Load (0.2ms) SELECT "users".* FROM "users" WHERE ("users"."id" = 3) LIMIT 1   AREL (0.4ms) UPDATE "users" SET "last_access" = '2011-08-14 18:37:42.858005', "updated_at" = '2011-08-14 18:37:42.858858' WHERE ("users"."id" = 3)   Event Load (0.6ms) SELECT "events".* FROM "events" WHERE ("events"."id" IN (5, 12, 20)) MULTI PARAMS EDIT : 3   AREL (1.9ms) UPDATE "events" SET "is_ten_event" = 'f' trying to make event is_ten_event = true   AREL (0.2ms) UPDATE "events" SET "is_ten_event" = 't', "updated_at" = '2011-08-14 18:37:42.913564' WHERE ("events"."id" = 5) trying to make event is_ten_event = true   AREL (0.1ms) UPDATE "events" SET "is_ten_event" = 't', "updated_at" = '2011-08-14 18:37:42.916311' WHERE ("events"."id" = 12) trying to make event is_ten_event = true   AREL (0.1ms) UPDATE "events" SET "is_ten_event" = 't', "updated_at" = '2011-08-14 18:37:42.918503' WHERE ("events"."id" = 20) Redirected to http://0.0.0.0:3000/admin/events/events

And here's the log output from the second submit (when it doesn't work)

Started POST "/admin/events/events/multi_params_edit" for 127.0.0.1 at Sun Aug 14 19:37:49 +0100 2011   Processing by Admin::Events::EventsController#multi_params_edit as HTML   Parameters: {"commit"=>"save changes (not functional)", "authenticity_token"=>"3MJ8aUhRWkrsOTLzkcLup8s7wrQH387H7uJeeKEU9Ss=", "utf8"=>"✓", "is_ten_event_ids"=>["5", "12", "20"]}   User Load (0.3ms) SELECT "users".* FROM "users" WHERE ("users"."id" = 3) LIMIT 1   AREL (0.4ms) UPDATE "users" SET "updated_at" = '2011-08-14 18:37:50.369619', "last_access" = '2011-08-14 18:37:50.368912' WHERE ("users"."id" = 3)   Event Load (0.6ms) SELECT "events".* FROM "events" WHERE ("events"."id" IN (5, 12, 20)) MULTI PARAMS EDIT : 3   AREL (1.9ms) UPDATE "events" SET "is_ten_event" = 'f' trying to make event is_ten_event = true trying to make event is_ten_event = true trying to make event is_ten_event = true Redirected to http://0.0.0.0:3000/admin/events/events

As you can see, in both cases, the 3 event ids which are checked get passed through, and the length of the @events array is 3. After all events are set to false, the first log staement shows the block being executed, and the database being updated. The second log statement shows that although the block was run (from the printout "trying to make event is_ten_event = true") the update_attribute call didn't do anything!

CAn anyone tell me why?? it seems very simple this, so probably doing something silly.

What is also odd however is that I wrapped the whole thing in a Transaction, which should ensure that if the update_attribute didn't work, the set all events to is_ten_event = false call should be rolled back, but this doesn't happen either!

I'm losing faith in transaction as a method, and update_attribute. I'm somewhat losing faith in reality!

Can anyone please help!??

2

Try doing it without any special effort in the controller. If you view source on a form page that Rails has generated with the form builder method check_box, you'll see that there's a hidden element generated before the checkbox, with the same name as the checkbox, and with the value=0. That takes care of your "un-checked checkboxes aren't submitted by the browser" problem for you, automagically. Your system (unless you are using hand-coded checkboxes) is redundant, and probably confusing to update_attributes.

Walter

3

Walter, thanks for helping,

"Try doing it without any special effort in the controller."

Not sure what you mean I should do, I understand what you're saying, but I'm not sure what the 'normal' / simple way to do this is.

This is what I've got in the controller after trying to simplify like you said:

def multi_params_edit

    @events = Event.find( params[:is_ten_event_ids] )     logger.debug("MULTI PARAMS EDIT : " + @events.length.to_s)

    @events.each do |e|         logger.debug("trying to make event is_ten_event = true")         e.update_attribute(:is_ten_event, true)     end

      redirect_to (:action =>:index)

    end

but this does what I was trying to avoid, and when I uncheck the box and submit, the attribute is not changed. the check returns! Could you possibly explain how I should do this in a little more detail please.

Thanks

4

It sounds like you're inside a different controller than the EventsController. Is that true?

Could you set this up with nested attributes?

class Foo    has_many :events    accepts_nested_attributes_for :events end

class Event    belongs_to :foo end

#FooController

def update    @foo = Foo.find(params[:id])    if @foo.update_attributes(params[:foo])      redirect_to @foo, :notice => 'Yay'    else      render :action => :edit    end end

foos/edit.html.erb

<%= form_for @foo do |f| %> ... regular Foo fields here ... <%= f.fields_for :events do |builder| %> <%= render "event_fields", :f => builder %> <% end %> ... rest of the form, including the submit ... <% end %>

foos/_event_fields.html.erb

... any other Event fields ... <%= f.check_box :is_ten_event %>

Now Foo can have as many Events as it needs, and each Event can have an is_ten_event checkbox with the magical un-check ability, and the controller can take care of everything in one submit, with no extra effort.

Unless I'm completely missing the point of your domain model, this should Just Work™.

Walter

5

I've got a table of events, and each event has a boolean attribute is_ten_event.

On each row of the table is a chekbox to edit the value of is_ten_event, so that multiple rows can be edited with one submit.

In order to allow boxes to be un-checked as well, the logic in the controller works like this

get array of events from checkboxes that are ticked. make all events.is_ten_event = false make all events in array . is_ten_event = true

When I first check the checkbox and submit, everything works fine, the attribute is updated in the database and the table view reflects the changes. If I then submit again, with the same values still checked the values I set the last time get set to false.

The problem is rails' change tracking. When you save a record, active record checks whether there are actually any changed attributes and saves those. You've loaded your events from the database, which have your flag set to true. Then you call update_all which changes everything to false in the database, but doesn't update any objects that already exist in memory, so when you call update attribute, rails thinks you are setting to true something that is already true and doesn't do anything.

Fred

6

@Walter

Actually the form being submitted is going through EventsController, the table of events is just the events/index, and I've made a new route called events/multi_params_edit, which is where the form submits to.

So the EventsController is trying to update lots of events, not an associated model.

Thanks for the advice though, it's actually helped somewhere else!

@Fred - Ok that makes sense, what would be the correct way to do this then?

Can I somehow set all to false all events, except those passed in as params? Or can I somehow force it to set the value to true even though it thinks it has done it already?

Thanks for the help