Silly Error!

Rails
1

What am I missing here?

Controller
def add_history
@history = History.new
Patient.find(params[:id]).history.create(params[:history])
flash[:notice] = “Added History”
redirect_to :action =>“show”, :id => params[:id]
end

Models
Patient
has_one :history
History
belongs_to :patients

when I try to add a History I get

You have a nil object when you didn’t expect it!
You might have expected an instance of ActiveRecord::Base.
The error occured while evaluating nil.create

2

On 6/15/07, Armitage [email protected] wrote:

end

You might have expected an instance of ActiveRecord::Base.
The error occured while evaluating nil.create

I believe your thinking that a has_one assocaition has a create method
like
a has_many. The has_one association works a bit different. Your patient
will have a create_history method instead. You could rewrite this as

from
def add_history
@history = History.new # Does nothing You don’t re-assign it.
Patient.find(params[:id]).history.create( params[:history])

  flash[:notice] = "Added History"
  redirect_to :action =>"show", :id => params[:id]
end

to

def add_history
@history = Patient.find( params[:id] ).create_history(
params[:history] )
|| History.new
flash[:notice] = “Added History”
redirect_to :action => “show”, :id => params[:id]
end

This will effectivley give the same functionality as you have.

You may want to add a bit of a rescue clause in the case that the
Patient is
not found. Or use find_by_id which doesn’t throw an Exception
immediatley,
but will when you call create_history on nil.

Hope that helps
Daniel

3

Thats perfect!

Thank you very much indeed