How do I force ActiveRecord to reload a class?

Question

I'm creating a bunch of migrations, some of which are standard "create table" or "modify table" migrations, and some of which modify data. I'm using my actual ActiveRecord models to modify the data, a la:

Blog.all.each do |blog|
  update_some_blog_attributes_to_match_new_schema
end

The problem is that if I load the Blog class, then modify the table, then use the Blog class again, the models have the old table definitions, and cannot save to the new table. Is there a way to reload the classes and their attribute definitions so I can reuse them?

Answer 1

答案是肯定的！

Blog.reset_column_information

Answer 2

I always used new models in migrations

    MyBlog < ActiveRecord::Base
      set_table_name 'blogs'
    end

    def self.up
      MyBlog.all.each do |blog|
        update_some_blog_attributes_to_match_new_schema
      end
    end

But Blog.reset_column_information is more convenient.

Answer 3

Create new instances:

---

Old_blogs = Blog.all

# change/modify db table in here

New_blogs = Blog.all # this should be reloaded or you could use the .reload on this

# change information, load old into new

ex.

Old_blogs.each do |blog|
  New_blogs.find(blog.id).title = blog.title
end