Validates :presence vs validates_presence_of using rails 3

ruby-on-rails-3

I have a couple of simple models that are associated like so:

MODELS

class Task < ActiveRecord::Base
  belongs_to :user
  validates :name, :presence => true, :message => 'Name cannot be blank, Task not saved'
end

class User < ActiveRecord::Base
  has_many :tasks
end

VIEW has a call in it like so:
user.tasks <– then I loop through the tasks

The Issue:

In the task model —

when I use:

validates :name, :presence => true ,  :message => 'Name cannot be blank, Task not saved'

I get a 500 error:

ActionView::Template::Error (uninitialized constant User::Task):
NameError in View file

when I use:

validates_presence_of :name

Everything works.

I thought the both validates methods above where the same…is the issue have to do with associations and how validation tie into associated models. I have a hunch that something is going on with the way things are associated, but it is just a hunch.

Any help will be appreciated. Thank very much.

Best Answer

When you use the newer validates :name format, you can put multiple validations in one line rather than having to have multiple lines for each type of validation. Because of this, when Rails hits your :message parameter, it thinks it's a validation method rather than a message associated with :presence. Try this instead:

validates :name, :presence => {:message => 'Name cannot be blank, Task not saved'}

Also, depending on how you display your errors, this error may actually show up as 'Name Name cannot be....'; if so, you'll want to set the message to just 'cannot be blank, Task not saved'.

Related Solutions

Ruby-on-rails – Rails: How to rename a database column in a Ruby on Rails migration

rename_column :table, :old_column, :new_column

You'll probably want to create a separate migration to do this. (Rename FixColumnName as you will.):

script/generate migration FixColumnName
# creates  db/migrate/xxxxxxxxxx_fix_column_name.rb

Then edit the migration to do your will:

# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
  def self.up
    rename_column :table_name, :old_column, :new_column
  end

  def self.down
    # rename back if you need or do something else or do nothing
  end
end

For Rails 3.1 use:

While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".

See "Active Record Migrations" for more information.

rails g migration FixColumnName

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:

rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...

You could use change_table to keep things a little neater:

class FixColumnNames < ActiveRecord::Migration
  def change
    change_table :table_name do |t|
      t.rename :old_column1, :new_column1
      t.rename :old_column2, :new_column2
      ...
    end
  end
end

Then just db:migrate as usual or however you go about your business.

For Rails 4:

While creating a Migration for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:

$ > rails g migration ChangeColumnName

which will create a migration file similar to:

class ChangeColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Rails 3: validates :presence => true vs validates_presence_of

All those validates_whatever_of :attr macros do is call validates :attr, :whatever => true.

The problem is you are using validate and not validates.

Best Answer

Related Solutions

Ruby-on-rails – Rails: How to rename a database column in a Ruby on Rails migration

Rails 3: validates :presence => true vs validates_presence_of

Related Topic