How to safely remove a column in Rails

Here is the text version:

# How to delete a column from a table

# Step 1️⃣: Set the column to ignored

class User < ActiveRecord::Base

self.ignored_columns = [:username]

end

# Trying to access the column will raise an error

u = User.first

u.username # raises NoMethodError

# Step 2️⃣: Change your code not to use any more that column

# Step 3️⃣: Deploy to production

# and monitor any NoMethodError errors reported

# Step 4️⃣: Add a migration to drop the column

# done