Why am I getting "undefined method" error?

ruby-talk
1

Hi,

I have a model, in which I have defined a method ...

class Form < ActiveRecord::Base
        has_many :form_items
        validates_associated :form_items

...

        def self.has_items
                FormItem.count(:all, :conditions => ["form_id
= ?", :id])
        end
end

but when i try and call this method from another class,

        def new
                @form = Form.find_by_user_id(session[:user_id])
                if (@form == nil)
                        false
                else
                        @form.has_items
                end
        end

I'm getting the error below:

undefined method `has_items' for #<Form:0xb78f5e3c>

Any ideas? Thanks, - Dave

2

You defined a class method, then used it on an instance. You want an
instance method, so remove self. from in front of the method
definition.

Also, you are passing a symbol instead of the actual id, so you'll
need to fix that too:

def has_items
    FormItem.count(:all, :conditions => ["form_id = ?", id])
end

-greg

···

On Sun, Aug 3, 2008 at 5:48 PM, laredotornado <laredotornado@zipmail.com> wrote:

Hi,

I have a model, in which I have defined a method ...

class Form < ActiveRecord::Base
       has_many :form_items
       validates_associated :form_items

...

       def self.has_items
               FormItem.count(:all, :conditions => ["form_id
= ?", :id])
       end
end

3

laredotornado wrote:

Hi,

I have a model, in which I have defined a method ...

class Form < ActiveRecord::Base
        has_many :form_items
        validates_associated :form_items

...

        def self.has_items
                FormItem.count(:all, :conditions => ["form_id
= ?", :id])
        end
end

but when i try and call this method from another class,

        def new
                @form = Form.find_by_user_id(session[:user_id])
                if (@form == nil)
                        false
                else
                        @form.has_items
                end
        end

I'm getting the error below:

undefined method `has_items' for #<Form:0xb78f5e3c>

Any ideas? Thanks, - Dave

By adding "self." to the has_items method definition, you've defined it as class method, but @form is an instance of Form. If you want to call has_items on an instance, remove the "self." in the method definition:

def has_items
    ...
end

···

--
RMagick: http://rmagick.rubyforge.org/

4

Hi,

       def self.has_items
               FormItem.count(:all, :conditions => ["form_id
= ?", :id])
       end
end

but when i try and call this method from another class,

       def new
               @form = Form.find_by_user_id(session[:user_id])
               if (@form == nil)
                       false
               else
                       @form.has_items
               end
       end

You've defined a class method but you're calling it on an instance (and it looks like it should by a instance method. You could also do away with it altogether and right

if @form
  @form.form_items.any?
else
  false
end

or even

@form && @form.form_items.any?

Fred

···

On 3 Aug 2008, at 22:48, laredotornado wrote:

Any ideas? Thanks, - Dave

5

laredotornado wrote:

but when i try and call this method from another class,

        def new

In Ruby, defining your own "new" method is rarely done. In Ruby, new is a class method that allocates a new instance of the class and then calls the "initialize" instance method to initialize the object. So, if you're wanting to define the instance method that gets called when you create a new instance of the class, define the initialize method:

class MyClass
    def initialize
       # initialization code
    end

    # other stuff in the class

end

···

--
RMagick: http://rmagick.rubyforge.org/