Rails - Jul 2006 - Sequencing control with edit method in CRUD examples

I have been playing with the cookbook type of tutorials building a fish 
tournament scoring piece and am having a bit of a problem with a DB 
field called "points" in my "catch" table that is not input
by the user
but is calulated based on a "size" field that is input by the user.

I have the following in my catch_controller.db

def new
@catch = Catch.new
@fish = Fish.find_all
@bait = Bait.find_all
end

def create
    @catch = Catch.new(@params[''catch''])
    @catch.datetime = DateTime.now
    @catch.points = @catch.size
		if @catch.bait_id == 2
			@catch.points = @catch.size + (@catch.size/10)
		end
		if @catch.bait_id == 3
			@catch.points = @catch.size + (@catch.size/5)
		end
    if @catch.save
        redirect_to :action => ''list''
    else
        render_action ''new''
    end
end

Granted it''s not particularly elegant but when a new catch is entered 
the "points" are correctly set in the create method. The problem I am 
having is in "Edit".

def edit
		@catch = Catch.find(@params["id"])
		@fish = Fish.find_all
		@bait = Bait.find_all


    @catch.points = @catch.size
		if @catch.bait_id == 2
			@catch.points = @catch.size + (@catch.size/10)
		end
		if @catch.bait_id == 3
			@catch.points = @catch.size + (@catch.size/5)
		end
    if @catch.save
        redirect_to :action => ''list''
    else
        render_action ''new''
    end
end

Where or in what method would I put similar code so that when someone 
edits the "size" field of a record the "points" are properly
tabulated?
The code above does not correctly work as it does for the new/create 
function. Should this code be in an update method? What runs after the 
edit view?

With default edit/update scaffolding I am seeing the "size" properly 
updated but no effect on "points". But if I then go back into the
record
with the edit view and "submit" with no further changes the
"points" are
magically updated. WTF is going on and how do I get my code to set the 
points in the proper place? Clearly it does not belong in the edit view 
...

-- 
Posted via http://www.ruby-forum.com/.

Nevermind, solved. But a real POS solution. Clearly I am missing 
something here.

def update
    @catch = Catch.find(params[:id])
    if @catch.update_attributes(params[:catch])
      @catch.points = @catch.size
      if @catch.bait_id == 2
         @catch.points = @catch.size + (@catch.size/10)
      end
      if @catch.bait_id == 3
         @catch.points = @catch.size + (@catch.size/5)
      end
      @catch.update_attributes(params[:catch])
      redirect_to :action => ''show'', :id => @catch
    else
      render :action => ''edit''
    end
end

By doing my points mod after the initial catch.update, then doing 
another catch.update it works OK. Not sure why I couldn''t just do my 
points processing before the first catch.update though -- that''s how it
should work. This method is invoked after the edit view (form) is 
submitted and the new score is input. I''m thinking that perhaps the new
score was input by the form, but the @catch instance is getting the old 
score value to assign to points (from the db model) not the new one that 
was freshly input inside the params. I bet there''s a way to extract it 
from the params and insert the updated score into the params[:catch] so 
that a single update can be done. Any ideas?


-- 
Posted via http://www.ruby-forum.com/.

Hey,
I see you solved your problem, but you really should put that
calculation in the model, not in the controller, then call it from the
controller.  This will keep your code clean and DRY, and makes it more
MVCish/Railsish.  You may want to just put it in a before_save filter in 
your model, would be simple, assuming on all saves you want to calculate 
points.  Look up callbacks in the api.  Good Luck!

Chris Carter
concentrationstudios.com

Mike Kogan wrote:
> I have been playing with the cookbook type of tutorials building a fish 
> tournament scoring piece and am having a bit of a problem with a DB 
> field called "points" in my "catch" table that is not
input by the user
> but is calulated based on a "size" field that is input by the
user.
> 
> I have the following in my catch_controller.db
> ...
> 
> Where or in what method would I put similar code so that when someone 
> edits the "size" field of a record the "points" are
properly tabulated?
> The code above does not correctly work as it does for the new/create 
> function. Should this code be in an update method? What runs after the 
> edit view?
> 
> With default edit/update scaffolding I am seeing the "size"
properly
> updated but no effect on "points". But if I then go back into the
record
> with the edit view and "submit" with no further changes the
"points" are
> magically updated. WTF is going on and how do I get my code to set the 
> points in the proper place? Clearly it does not belong in the edit view 
> ...
-- 
Posted via http://www.ruby-forum.com/.

Thanks Chris -- so move the points tabulation code (which I do want on 
all catch saves whether a new catch is entered or an existing one is 
edited/updated) to the model but still invokve it from the controller? I 
was under the impression actions not related to displaying data should 
be in the controller MVC-wise etc.

Will a before-save filter be invoked on both new and edit operations 
automatically or do I need to enable this? I''ll research the callbacks 
and before_save later.

Also I am wondering about my "solution" -- there really should not
have
to be 2 calls to update_attributes should there? Does the before_save 
get invoked through a callback when the update_attributes or save 
methods are invoked? That would be a lot cleaner.

Thanks again,
Mike


Chris Carter wrote:
> Hey,
> I see you solved your problem, but you really should put that
> calculation in the model, not in the controller, then call it from the
> controller.  This will keep your code clean and DRY, and makes it more
> MVCish/Railsish.  You may want to just put it in a before_save filter in 
> your model, would be simple, assuming on all saves you want to calculate 
> points.  Look up callbacks in the api.  Good Luck!
> 
> Chris Carter
> concentrationstudios.com
> 
-- 
Posted via http://www.ruby-forum.com/.

Mike Kogan wrote:
> Thanks Chris -- so move the points tabulation code (which I do want on 
> all catch saves whether a new catch is entered or an existing one is 
> edited/updated) to the model but still invokve it from the controller? I 
> was under the impression actions not related to displaying data should 
> be in the controller MVC-wise etc.
> 
> Will a before-save filter be invoked on both new and edit operations 
> automatically or do I need to enable this? I''ll research the
callbacks
> and before_save later.
> 
> Also I am wondering about my "solution" -- there really should
not have
> to be 2 calls to update_attributes should there? Does the before_save 
> get invoked through a callback when the update_attributes or save 
> methods are invoked? That would be a lot cleaner.
> 
> Thanks again,
> Mike
> 
> 
> Chris Carter wrote:
>> Hey,
>> I see you solved your problem, but you really should put that
>> calculation in the model, not in the controller, then call it from the
>> controller.  This will keep your code clean and DRY, and makes it more
>> MVCish/Railsish.  You may want to just put it in a before_save filter
in
>> your model, would be simple, assuming on all saves you want to
calculate
>> points.  Look up callbacks in the api.  Good Luck!
If the scoring rules are fixed, you can just compute the points on 
demand, rather than saving them in the database. E.g. (in Catch)

   BAIT_SCALE_FACTORS = [1.0, 1.0, 1.1, 1.2]

   def points
     size * BAIT_SCALE_FACTORS[bait_id]
   end

(untested!) You might need to add some protection against size or 
bait_id being undefined (but the same would be true of your original code)

   Justin

Justin thanks for that idea. However I think I am going to store them 
because there will be multiple fish per angler and ultimately I will be 
computing the angler''s total points from all catches etc. So for 
simplicity I really want to store the points although I like your 
approach better -- being a 25+ year C programmer I don''t have my teeth 
around the Ruby syntax yet to do the obvious as you did with the points 
method and array. I think I''ll be doing that anyway to better isolate 
the common points logic.

Thanks!


-- 
Posted via http://www.ruby-forum.com/.

Totally cool guys, I really appreciate all the pointers. The before-save 
callback works like a charm once the moronic programmer realizes the 
method goes in the model not the controller ;) Justin I took your advice 
a step further, and put the bait scale factors into the bait table so it 
wouldn''t be hard-coded anywhere and would always be data-driven for 
other tournaments, bait types, and potential point scaling factors 
related to bait type.

The only thing that bites is my lack of understanding why the original 
piece of code in the 2nd post was required to have 2 updates. When I 
figure that out I''ll be much further down the road to understanding
more
about data passing and flow control in RoR.

Thanks Again, even an old OS programmer can find a little joy in this 
MVC stuff!

-- 
Posted via http://www.ruby-forum.com/.

Mike Kogan wrote:
> Totally cool guys, I really appreciate all the pointers. The before-save 
> callback works like a charm once the moronic programmer realizes the 
> method goes in the model not the controller ;) Justin I took your advice 
> a step further, and put the bait scale factors into the bait table so it 
> wouldn''t be hard-coded anywhere and would always be data-driven
for
> other tournaments, bait types, and potential point scaling factors 
> related to bait type.
> 
> The only thing that bites is my lack of understanding why the original 
> piece of code in the 2nd post was required to have 2 updates. When I 
> figure that out I''ll be much further down the road to
understanding more
> about data passing and flow control in RoR.
> 
> Thanks Again, even an old OS programmer can find a little joy in this 
> MVC stuff!
Hi Mike!
Glad to see it all worked out.  It needed two updates because you 
updated them from the edit, then made the points, then updated again. 
If you did the points logic outside of that if statement you would have 
only needed the one.

--
Chris

-- 
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