Question

I have a profile model, and a user has_one profile.

Here’s my route:

resources :users
resources :profiles

Here’s the show method in my controller:

def show
  @profile = @user.profile
end

Why do I get this error when I try to access the show view:

NoMethodError in ProfilesController#show

undefined method `profile' for nil:NilClass

Answer 1

You need to initialize the @user instance variable. You probably want to do something like this:

def show
  @user = User.find(params[:id])
  @profile = @user.profile
end

Boring explanation: Instance variables (the ones with @ in the front) are nil by default. They can be de facto “instantiated” by just assigning a non-nil value to it. Here, @user is an instance variable, and it points to nil because it hasn’t been assigned anything. profile is invoked in the context of nil, which doesn’t have a profile method, so you get the no method exception. This is as opposed to local variables, starting with a lower-cased letter, which would in this case have raised a local variable not found exception.