Rails getting single values from request

Question

in Rails the create method in a Controller by default receives an HTTP request with different values. By default new records are created like this:

@apo = Apo.new(params[:apo])

But how can i access single Values from this params hash?

I would like to create something like this:

@apo = Apo.new do |a|
        a.name = $someVariable
        a.value = $anotherVariable
        a.quantity = -> here i want to have one value which is in params[:apo]
        end

Do you understand what i´m looking for? Tried million possibilities but it just doesn´t work.

Alternatively, is it possible, to create a second params hash in the view, which only saves this one value?

P.S. i don´t want to use JavaScript for doing this...

Thanks a lot!

Answer 1

params is special, and is set by Rails for each HTTP request. It's a hash in the form

{ :object => { :attrib1 => "value1", :attrib2 => "value2" ... }}

So you can reference the entire object with

params[:foo]

and individual attributes (fields) like

params[:foo][:bar]

A ActiveRecord model can be created in one call by passing a hash of values, as in your first example. But there are many other ways to create an instance. You can

def make_apo(some_value, another_value)
  apo = Apo.new
  apo.name = some_value
  apo.value = another_value
end

Such a method will return an instance of Apo. In your case, if you have some values in params, change the above to accept params as another argument, or pass specific values when you call.

def make_apo(some_value, another_value, quantity, passed_params)
  apo = Apo.new
  apo.name = some_value
  apo.value = another_value
  apo.quantity = passed_params[:apo][:quantity]
end

But this is all a pretty unusual way of going about things. So don't just do this -- it's more by way of explaining what's going on than suggesting that you do this.