Add named_scopes dynamically in rails application

Question

Just like dynamic finder methods in rails, is there any way to have dynamic finder methods for associated models?

Consider the following models

class User
   attr_accessible :name, :phone_no
   has_many :notes
end

class Note
   belongs_to :user
   attr_acccessible :note
end

How can I call a dynamic finder of note attribute from the User object?

What are your Rails/Ruby versisons? – Andrei Aug 10 '12 at 13:55 — Andrei, Aug 10 '12 at 13:55
Ruby version: 1.8.7 Rails Version: 3.0.4 beta – Kashif Umair Liaqat Aug 11 '12 at 04:08 — Kashif Umair Liaqat, Aug 11 '12 at 04:08

score 1 · Accepted Answer · answered Aug 10 '12 at 14:23

1

Scopes are class methods, so User.scope_name (more on scopes here: http://guides.rubyonrails.org/active_record_querying.html#scopes). If you want to find a specific note that belongs to that user object, you could define an instance method - something like this:

def note_with_content(content_string)
   self.notes.where(:content => "#{content_string}")
end

or

def last_note
   self.notes.last
end

And use it the following way:

@user.note_with_content("This is a note")

@user.last_note

answered Aug 10 '12 at 14:23

Andrei

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Hmm your answer is good, but what if I have to add these instance methods dynamically? Suppose a new attribute is added to Note class dynamically then I want to provide an instance method for that attribute as well. How can I do that dynamically? – Kashif Umair Liaqat Aug 11 '12 at 04:12
`def note_with_attribute(attribute_name, value)` // `self.notes.where("#{attribute_name}" => "#{value}")`// `end` – Andrei Aug 11 '12 at 15:49
^^^ You could always pass in the name of the attribute to search by – Andrei Aug 11 '12 at 15:52
That sounds great... I will try it. – Kashif Umair Liaqat Aug 12 '12 at 04:47

Add named_scopes dynamically in rails application

1 Answers1