Instance variable?

Rails
1

I’m trying to grab a temporary variable from my view and then pass along
that value to my model

My view code is this:

<%= text_field 'product', 'qty_added', {:size=>3}

And I’m trying to pass the qty_added variable to my model.
item.quantity = qty_added

It doesn’t seem to be working… I’m sure I’m missing many fundamental
things but if somebody could start me down the correct path…

Thx…

2

Vince:

There is probably some clever way of doing what you ask. For myself,
controllers are the middlemen, so my views talk to my controllers and
my controllers talk to my model. Does that help?

bruce

3

There is probably some clever way of doing what you ask. For myself,
controllers are the middlemen, so my views talk to my controllers and
my controllers talk to my model. Does that help?

Hi Bruce,

I’m very new to the whole programming thing so yes it does help. I’m
still kind of lost though…

In this line,

<%= text_field ‘product’,
‘qty_added’,
{:size=>3}

I don’t even seem to be correctly capturing any data. I have a
display_cart.rhtml file where I print the value of that variable using

<%= @qty_added.inspect %>

But that always comes up as ‘nil’

I figure once I get the qty_added stored correctly I can then work on
the controller. Does that sound right?

4

One piece of added information to the mix. I think the big issue is
that where I submit the data I am not passing the qty_added. Here is
that relevant code:

    <%= link_to 'Add to Cart',
                {:action => 'add_to_cart', :id => product },
                :class => 'addtocart' %><br/>

I’ve defined the form like this:

<%=
text_field ‘product’, ‘qty_added’, {:size=>3}

What should I modify in the ‘Add to Cart’ link to also capture the
quantity?

5

This code implies that you are using a GET method to submit your data.
Even inside a form, a link_to will create an <a href … > link. Look at
your logs (log/development.log) and see what the params hash has in it
when the action is invoked (you are running tail -f log/development.log,
right? :).

If I understand the original problem, you have a “meta-field” called
qty_added that is not a database column. Its behavior is to exist solely
to add to the quantity column that is in the database. Rails won’t
automatically know what to do when that unknown field comes back in the
params hash, so you will have to manually extract it and stuff it in the
model. E.g.

controller code

def addtocart
thingie = Thing.find(params[:id])
thingie.quantity += params[:product][‘qty_added’] # assuming you
wanted to add…
begin
thingie.save!
rescue
# take some corrective action.
end
end

Alternatively, you can define the behavior in your model by adding
accessors for qty_added and making the write accessor add to quantity.

Does this help? Does anyone else have thoughts on this?

Vince W. wrote:

One piece of added information to the mix. I think the big issue is
that where I submit the data I am not passing the qty_added. Here is
that relevant code:

    <%= link_to 'Add to Cart',
                {:action => 'add_to_cart', :id => product },
                :class => 'addtocart' %><br/>

I’ve defined the form like this:

<%=
text_field ‘product’, ‘qty_added’, {:size=>3}

What should I modify in the ‘Add to Cart’ link to also capture the
quantity?

6

Steve R. wrote:

This code implies that you are using a GET method to submit your data.
Even inside a form, a link_to will create an <a href … > link. Look at
your logs (log/development.log) and see what the params hash has in it
when the action is invoked (you are running tail -f log/development.log,
right? :).

I suppose it is a get. I tried using a form instead just to see if it
would help, but I’m having trouble accessing variables from database in
the form. For instance, in _form.rhtml I have code that says:

<%= h(product.title) %>

But that simple code gives me an “undefined local variable or method
`product’ for #<#Class:0x4081f164:0x4081f0b0>” error

If I understand the original problem, you have a “meta-field” called
qty_added that is not a database column.

That’s correct. In my original model I had a line setting quantity
manually. i.e. item.quantity = 1. I want to change that to
item.quantity = qty_added but can’t seem to pass the variable to my
controller.

Its behavior is to exist solely
to add to the quantity column that is in the database. Rails won’t
automatically know what to do when that unknown field comes back in the
params hash, so you will have to manually extract it and stuff it in the
model. E.g.

controller code

def addtocart
thingie = Thing.find(params[:id])
thingie.quantity += params[:product][‘qty_added’] # assuming you
wanted to add…
begin
thingie.save!
rescue
# take some corrective action.
end
end

I tried the above but got an undefined method quantity error. I then
tried adding attr_accessor to my models for both product.rb and
line_item.rb but that didn’t solve it. Couldn’t really figure out where
to define quantity to make it happy.

Alternatively, you can define the behavior in your model by adding
accessors for qty_added and making the write accessor add to quantity.

I would be happy to try this too… really I’m just looking for the
easiest solution. :ol

Does this help? Does anyone else have thoughts on this?

I’m starting to understand things better… I appreciate your help…
please keep throwing suggestions at me!!!

-Vince