Rails help ActionView::Template::Error HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts

问题

My rails app runs fine on my locale machine with mysql. But on Heroku I get the following error: http://pastie.org/1697772

My kategoris_helper:

module KategorisHelper
def sortkat(column, title = nil)
  title ||= column.titleize
  css_class = column == sort_column ? "current #{sort_direction}" : nil
  direction = column == sort_column && sort_direction == "asc" ? "desc" : "asc"
  link_to title, {:sort => column, :direction => direction}, {:class => css_class}
end
end

My Kategoris controller:

class KategorisController < ApplicationController
    @kategori = Kategori.find(:first, :conditions => "cached_slug = '#{params[:id]}'")
    @konkurrencer = @kategori.konkurrancers.order(sort_column + " " + sort_direction)
    @titel = @kategori.name
  end

private

def sort_column
  Konkurrancer.column_names.include?(params[:sort]) ? params[:sort] : "created_at"
end

  def sort_direction
    %w[desc asc].include?(params[:direction]) ? params[:direction] : "desc"
  end
end

My models:

class Kategori < ActiveRecord::Base
    has_many :konkurrancers
    has_friendly_id :name, :use_slug => true
end

class Konkurrancer < ActiveRecord::Base
    belongs_to :kategori
    has_friendly_id :name, :use_slug => true
end

回答1:

PostgreSQL is unforgiving my kategori_id was varchar.

Changed it to be an integer. Problem solved.

回答2:

Here is your problem:

  css_class = column == sort_column ? "current #{sort_direction}" : nil
  direction = column == sort_column && sort_direction == "asc" ? "desc" : "asc

I'm not quite sure what your doing here but I think the error is coming from you using = and == on the same line. Your setting a variable that is comparing itself to another variable.

You ned to change it so you don't have == in there.

来源：https://stackoverflow.com/questions/5384982/rails-help-actionviewtemplateerror-hint-no-operator-matches-the-given-name