Ruby On Rails Change Column to Null, Not Work?

Question

I command in Terminal to change on column in database to not null, but It seems not work.

rails g migration change_column_null :Speaker, :surname, false

I got a file ChangeColumnNull But inside, it is nothing.

class ChangeColumnNull < ActiveRecord::Migration
def change
end
end

Lecture Controller (Def Create):

class CplecturesController < ApplicationController
layout 'cp_layout'

 def create
@lecture = Lecture.new(lecture_params)

@lecture.save
redirect_to @lecture
end

private
def lecture_params
  params.require(:lecture).permit(:lecture_title, :lecture_day,   :column, :start_time, :end_time, :registered_speakers, :guest_speakers, :description)
end
end

Forms

 <%= form_for :lecture, url:lectures_path do |f| %>
 <form>
 <div class="form-group">
  <%=label_tag "Lecture Title" %><br>
  <%= f.text_field :lecture_title, :class => "form-control",   :placeholder => "Example: Why is Wordpress the best?" %>
</div>

This looks like a duplicate of: stackoverflow.com/questions/5966840/… — GoGoCarl
– GoGoCarl, Commented Apr 25, 2016 at 21:03

toddmetheny · Accepted Answer · 2016-04-26 03:17:50Z

6

Erase that migration and write a blank migration with a better name and then fill it out by setting a default value. If you have a default value it will never be null.

rails g migration ChangeColumnOnTableName

Then inside that migration do the following:

change_column :name_of_table, :name_of_column, :data_type_of_column, :null => false

If you're only worried about it being null based on what a user enters, you could simply add a validation that requires it. In your model:

validates :name_of_column, presence: true

edited Apr 26, 2016 at 3:17

answered Apr 25, 2016 at 20:58

toddmetheny

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25 Comments

Joe Over a year ago

va185042:project Nixon$ rails g nameNull change_column :Speaker, :organisation, :string, :default => false va185042:project Nixon$ bundle exec rake db:migrate Nothing to annotate. After I command this, nothing happen, not even file...

GoGoCarl Over a year ago

+1 for the validation in the model, but why use a default value instead of null: false? Wouldn't you prefer to fail if data was input without a required field, rather than storing potentially garbage data with a guessed default?

toddmetheny Over a year ago

@Joe that change_column goes inside the migration. Not as part of the migration command. You run them separately. I will update to show you.

toddmetheny Over a year ago

@GoGoCarl valid point. depends on why you don't want it to be null. We don't really have that information. If it's a boolean field, for instance, I think you might naturally want it to be true or false instead of enforced. But don't disagree in principle. That works, too.

tadman Over a year ago

As a note, modern Rails recommends validates :name_of_column, presence: true instead of the legacy style.

|

Manjunath Reddy · Accepted Answer · 2018-09-06 15:27:34Z

1

if you are using latest ruby (2.5+) Here is the migration script to change fields from NOT NULL to NULL

class ChangeEmailPasswordToNullableUsers < ActiveRecord::Migration[5.2] def change change_column_null :users, :email, true change_column_null :users, :password, true end end

answered Sep 6, 2018 at 15:27

Manjunath Reddy

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