NOOB Question on Instance Variable

I have a class photo. It belongs_to a project.

In my ProjectsController I am creating 2 instance variables:

@displayphoto = Photo.find_by_project_id(params[:id])

…and also

@photo = @project.build_photo

The @displayphoto instance returns a nil object.
However,

@photo = Photo.find_by_project_id(params[:id])

works fine. So evidently it is the name @displayphoto
that is causing the problem.

So I have 2 questions:

  1. Must an instance variable always be the same
    name as the name of the class?
  2. If the above is true, how can I create 2 separate
    instance variables in my controller for the same class?

Thanks,

Jet

Jet Thompson wrote:

I have a class photo. It belongs_to a project.

In my ProjectsController I am creating 2 instance variables:

@displayphoto = Photo.find_by_project_id(params[:id])

…and also

@photo = @project.build_photo

The @displayphoto instance returns a nil object.
However,

@photo = Photo.find_by_project_id(params[:id])

works fine. So evidently it is the name @displayphoto
that is causing the problem.

So I have 2 questions:

  1. Must an instance variable always be the same
    name as the name of the class?

No. An instance variable is just a variable (scoped to the instance of
it’s class). And ivar can reference any object.

  1. If the above is true, how can I create 2 separate
    instance variables in my controller for the same class?

Just as you attempted to do. There is obviously something else going on
here that can’t be seen from the code you provided. Or, the value of
params[:id] is different between your two example.

2010/1/12 Robert W. [email protected]:

here that can’t be seen from the code you provided. Or, the value of
params[:id] is different between your two example.

One place to look for clues is in development.log, that will show you
the params values and the queries run so you can check the id is
correct.

If you still can’t find it have a look at the Rails Guide on debugging
and break in to the failing point using ruby-debug to inspect the
variables and see what is going on.

Colin

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