i am getting override method issue in compute_public_path' for module `ActionView::Helpers::AssetTagHelper'

Hi All,

I am doing migration rails 3.0.5 to 3.2.3 and also changed ruby
versions from 1.8.7 to 1.9.3.

I want override the method
compute_public_path(ActionView::Helpers::AssetTagHelper).

Now i got this error while migrating the application (3.2.3).

`alias_method': undefined method `compute_public_path' for module
`ActionView::Helpers::AssetTagHelper' (NameError)

Please give me your valuable suggestions the above issue.

I have done small program. it is working perfectly.

class String

    alias_method :old_to_s, :to_s

    def to_s
        if self=="one"
          "coming if "
        else
         "coming else"
        end

    end

end

str=String.new("one")
p str.to_s

p str.old_to_s