Since I am new to Rails, I am following this 'getting started' guide on rails website.
On section 6.1 Generating a Model, I should run rails generate model Comment commenter:string body:text post:references to get a comment model.
Supposedly, this is what should be included in the migration file:
class CreateComments < ActiveRecord::Migration
def change
create_table :comments do |t|
t.string :commenter
t.text :body
t.references :post
t.timestamps
end
add_index :comments, :post_id
end
end
But in my migration file, I have everything but this line add_index :comments, :post_id.
Instead, I have index:true following the t.references :post
I can't seem to find an explanation to this, can anyone explain to me what is going on here? Because later on I need to use :post_id, but in my version of migration, it is not clearly declared. I am very confused.
class CreateComments < ActiveRecord::Migration
def change
create_table :comments do |t|
t.string :commenter
t.text :body
t.references :post
t.timestamps
end
add_index :comments, :post_id
end
end
and
class CreateComments < ActiveRecord::Migration
def change
create_table :comments do |t|
t.string :commenter
t.text :body
t.references :post, index: true
t.timestamps
end
end
end
will do same things, both of them will add index to post_id column
also you can later add index to any column any column that you want to add to your model like
$ rails generate migration AddPartNumberToProducts part_number:string:index
that will produce this code:
class AddPartNumberToProducts < ActiveRecord::Migration
def change
add_column :products, :part_number, :string
add_index :products, :part_number
end
end
in above code if you want to create index for post_id then write it as t.integer :post_id
else you can try this add_index :comments, :post
Related
I have two models 'Tutorial' and 'Tutorialcategory'
class Tutorialcategory < ActiveRecord::Base
has_many :tutorials
class Tutorial < ActiveRecord::Base
belongs_to :tutorialcategory
Tutorials are associated with multiple categories like html,rubyonrails where html and ruby on rails are tutorialcategories
followings are migrations
class CreateTutorials < ActiveRecord::Migration
def change
create_table :tutorials,force: true do |t|
t.string :title
t.text :body
t.integer :rating
t.string :videoid
t.belongs_to :tutorialcategory
t.timestamps
end
end
end
class CreateTutorialcategories < ActiveRecord::Migration
def change
create_table :tutorialcategories do |t|
t.string :title
t.timestamps null:false
end
end
end
All tutorials are listing properly on index page but when I see category page it gives me following error
PG::Error: ERROR: column tutorials.tutorialcategory_id does not exist
I have no idea why you named your model Tutorialcategory instead of TutorialCategory which follow Rails naming convention and make it easier to understand.
Firstly, rollback your db one step
rake db:rollback
Change your migration file to:
class CreateTutorials < ActiveRecord::Migration
def change
create_table :tutorials,force: true do |t|
t.string :title
t.text :body
t.integer :rating
t.string :videoid
t.belongs_to :tutorial_category, index: true
t.timestamps
end
end
end
class CreateTutorialCategories < ActiveRecord::Migration
def change
create_table :tutorial_categories do |t|
t.string :title
t.timestamps null:false
end
end
end
Run the migration again and edit your model to match with new schema.
class TutorialCategory < ActiveRecord::Base
has_many :tutorials
class Tutorial < ActiveRecord::Base
belongs_to :tutorial_category
I have gone through some of similar question people asked but couldn't find the appropriate solution for it. I have also seen some people using this method - add_foreign_key
class CreateTaskLists < ActiveRecord::Migration
def change
create_table :task_lists do |t|
t.string :name
t.references :user
t.timestamps
end
add_foreign_key :task_lists, :users
end
end
but it is throwing undefined method error.
undefined method `add_foreign_key' for
#<CreateTaskLists:0x007ffe9a5cd578>
/Users/sushilkumar/.rvm/gems/ruby-2.2.3/gems/
activerecord-4.0.0/lib/active_record/
migration.rb:624:in `block in method_missing'
How to add foreign key in rails migration with different table name
I don't know, How does this work for them?
You can simply try this way using references
class CreateTaskLists < ActiveRecord::Migration
def change
create_table :task_lists do |t|
t.string :name
t.references :user, index: true
t.timestamps
end
add_foreign_key :task_lists, :users
end
end
class CreateTaskLists < ActiveRecord::Migration
def change
create_table :task_lists do |t|
t.string :name
t.references :user, index: true
t.timestamps
end
add_foreign_key :task_lists, :users
end
end
try this
Did you meant to reference the table User and not Users? If so, you must use the singular (:user) when making a reference:
class CreateTaskLists < ActiveRecord::Migration
def change
create_table :task_lists do |t|
t.string :name
t.references :user
t.timestamps
end
add_foreign_key :task_lists, :users
end
end
Hope this will work for you.
class CreateTaskLists < ActiveRecord::Migration
def change
create_table :task_lists do |t|
t.string :name
t.references :user
t.timestamps
end
add_foreign_key :users, :task_lists
end
end
So I am trying to create three models, Project, Entry and User. A Project has many Entries, and a a User has many Entries. I scaffolded the above three models with the following commands:
rails g scaffold Project title:string
rails g scaffold Entry project:project_id entry_for:user_id created_by:userid \
date:string start_time:string end_time:string total:string type_of_work:string \
on_off_site:string phase:string description:text
rails g scaffold User name:string
I realize that I probably totally goofed up the part where I manually put in the foreign keys for the other tables in the Entry model. I don't know how much has_many belongs_to automates the relationship between different models in terms of keys so I tried to add the foreign key fields manually. Is this wrong?
When I try to run db:migrate I get the following error:
undefined method `user_id' for #<ActiveRecord::ConnectionAdapters::TableDefinition:0x007fc1bdf37970>
Here are my migrations, as I tried to remove all of the foreign key fields but got the above error.
class CreateProjects < ActiveRecord::Migration
def change
create_table :projects do |t|
t.string :name
t.timestamps
end
end
end
class CreateEntries < ActiveRecord::Migration
def change
create_table :entries do |t|
t.string :project
t.string :project_id
t.user_id :entry_for
t.user_id :created_by
t.string :date
t.string :start_time
t.string :end_time
t.string :total
t.string :type_of_work
t.string :on_off_site
t.string :phase
t.text :description
t.timestamps
end
end
end
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :name
t.timestamps
end
end
end
class RemoveColumns < ActiveRecord::Migration
def self.up
remove_column :entries, :created_by
remove_column :entries, :entry_for
remove_column :entries, :project_id
end
def self.down
add_column :entries, :created_by, :user_id
add_column :entries, :entry_for , :user_id
add_column :entries, :project_id, :string
end
end
Thank you for your help!
In your migrations, instead of t.user_id you can try t.integer or t.index. That should at least get your migrations running.
I am going to use t.references entry_for and then write belongs_to :entry_for, class_name: "User" in the Entry model as a means of writing my own foreign key name. For the project column in entries I realized I can similarly write t.references project.
I want to add to my model Treatment an column, so that it belongs_to a category:
class CreateTreatments < ActiveRecord::Migration
def change
create_table :treatments do |t|
t.string :typ
t.string :content
t.date :day
t.references :patient
t.timestamps
end
add_index :treatments, :patient_id
add_index :treatments, :category_id
end
end
i want to add:
t.references :category
and
add_index :treatments, :category_id
I tried it simply copying it in and running a migration but it didnt`t worked! I know normally i would simply make an
rails g model Treatment category:references
How can i achieve this afterwards?
You should generate another migration:
rails g migration add_category_id_to_treatments category_id:integer
You ought to edit automatically generated migration and add line on the end of change method:
add_index :treatments, :category_id
Then you should run migration.
I have one table called profiles with some columns.
Now I wish to add a few columns to this table using the change-method in rails 3.1. I created a migration with the following code:
def change
change_table :profiles do |t|
t.string :photo
t.string :name
t.references :user
end
end
The migration works perfectly, but when I want to rollback I get
SQLite3::SQLException: duplicate column name: photo: ALTER TABLE "profiles" ADD "photo" varchar(255)
Any ideas why?
The auto-generated migrations for adding columns in Rails 3.1 is in the format:
class AddColumnToTable < ActiveRecord::Migration
def change
add_column :table, :column, :type
end
end
Perhaps try that syntax?
It looks like you need to tell the migration how to revert itself:
def change
change_table :profiles do |t|
t.string :photo
t.string :name
t.references :user
end
reversible do |dir|
dir.down do
remove_column :profiles, :photo
remove_column :profiles, :name
remove_column :profiles, :user_id
end
end
end
See http://guides.rubyonrails.org/migrations.html#using-reversible for more information.
Alternatively you could try using the old up and down methods which are still available like so:
def up
change_table :profiles do |t|
t.string :photo
t.string :name
t.references :user
end
end
def down
remove_column :profiles, :photo
remove_column :profiles, :name
remove_column :profiles, :user_id
end
More on up/down here: http://guides.rubyonrails.org/migrations.html#using-the-up-down-methods