Silly Error!

rubyonrails-talk
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

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

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