Puzzled with form on multiple table rows

Rails
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

On Aug 14, 2011, at 2:58 PM, Michael B. wrote:

get array of events from checkboxes that are ticked.
The view code looks like this :

HTML
(“events”.“id” IN (5, 12, 20))
trying to make event is_ten_event = true
Sun Aug 14 19:37:49 +0100 2011
(“users”.“id” = 3)
As you can see, in both cases, the 3 event ids which are checked get

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!??

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

On Aug 14, 7:58 pm, Michael B. [email protected] wrote:

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

5

On Aug 14, 2011, at 5:31 PM, Michael B. wrote:

you said:

 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.

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

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