如何查找具有主键的对象是 rails 上的字符串

Question

I has a table Reading(ID:string(8),title:string(100),contents:text) And in Reading models:

class Reading < ActiveRecord::Base
  self.table_name = "reading"
  self.primary_key = :ID
end

In reading controller

private
    # Use callbacks to share common setup or constraints between actions.
    def set_reading
      @reading = Reading.find(params[:ID])
    end

I have a record of reading table with ID is "20150910".

But Reading.find("20150910") not work.

Answer 1

You should look up about uuids - this is supported by default in Rails 4 ; it's essentially the same functionality you're seeking.

We do it:

If you've set the primary_key in your model, and have it set in your db:

execute "ALTER TABLE nodes ADD PRIMARY KEY (uuid);"

... you should be able to use the find method with the passed string quite simply:

 @reading = Reading.find params[:id]

--

As stated in the comments, the issue you have could be to do with the parameter you're passing through your routes. If you're not setting ID explicitly, you'll have to deal with :id :

#config/routes.rb
resources :readings, param: "ID"

Answer 2

Rails expects by default for the primary key to be an int called "id" (notice the lower case). You will need to override this default and set a new primary key. Here is a helpful blog post that explains the process better than I can here: http://ruby-journal.com/how-to-override-default-primary-key-id-in-rails/

Edit: I believe the detail you might be missing is that you need to make ID unique and not null in the database.