how to generate barcode in c# net with example by looking for the self prefix. For more about Ruby classes, see Appendix A. in Font

Generator QR Code in Font by looking for the self prefix. For more about Ruby classes, see Appendix A.

by looking for the self prefix. For more about Ruby classes, see Appendix A.
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We ve gone ahead and filled out the details for you. Without having seen a migration before, you should be able to tell exactly what s going on by looking at Listing 3-3.
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Listing 3-3. Completed db/migrate/001_create_events File
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class CreateEvents < ActiveRecord::Migration def self.up create_table :events do |t| t.column :title, :string t.column :location, :string t.column :occurs_on, :date end end
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CHAPTER 3 GETTING SOMETHING RUNNING
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def self.down drop_table :events end end
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Let s step through the code. First, we use the create_table method, giving it the name of the table we want to create. Inside the code block, we use the column method to create columns in the table. The column method takes the name of the column and its type. (For a full description of the available field types you can create in your migrations, see http://api.rubyonrails.org/classes/ActiveRecord/Migration.html.) On its own, this migration does nothing. Really, it s just a plain-old Ruby class. If we want it to do some work and create a table in the database for us, we need to run it. To run a migration, you use the built-in Rake task that Rails provides called db:migrate.
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Note Rake is a build language for Ruby. Rails uses Rake to automate several tasks, such as running
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database migrations, running tests, and updating Rails support files. You can think of Rake tasks as little utility programs. For a list of all available Rake tasks, run rake -T from your Rails project directory. For more information about Rake, including complete documentation, see http://rake.rubyforge.org/.
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From the command line, type the following to run the migration and create the
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events table. You ll recognize this command as the same one we used to test the database
connection. We sort of hijacked it for our test, knowing that it will attempt to connect to the database and thus prove whether the connection works. Since there were no existing migrations when we first ran it, it didn t do anything. Now that we have our first migration, running, it will result in a table being created.
$ rake db:migrate
== CreateEvents: migrating ================================================== -- create_table(:events) -> 0.0314s == CreateEvents: migrated (0.0316s) =========================================
Just as the output says, the migration created a new table. If you were to try to run the migration again (go ahead, try it!), you would see that nothing happens. That s because Rails keeps track of the current migration version and it knows that you re at version 1, so there s nothing left to do.
CHAPTER 3 GETTING SOMETHING RUNNING
Generating a Controller
We ve created a model and its supporting database table, so our next step is to work on the controller and view side of the application. We ll create a controller named (wait for it) events to control the operation of the events functionality of the application. Just as with models, Rails provides a generator that we can use to create controllers. Let s start using it.
$ ./script/generate controller events
exists exists create create create create create
app/controllers/ app/helpers/ app/views/events test/functional/ app/controllers/events_controller.rb test/functional/events_controller_test.rb app/helpers/events_helper.rb
The controller generator created three files: app/controllers/events_controller.rb: The controller that will be responsible for handling requests and responses for anything to do with events. test/functional/events_controller_test.rb: The class that will contain all functional tests for the events controller (we ll cover testing applications in 8). app/helpers/events_helper.rb: The helper class in which you can add utility methods that can be used in your views. The controller generator also created an empty directory in app/views called events. This is where we ll place the templates for the events controller.
Up and Running with Scaffolding
One of the killer features that gave a lot of exposure to Rails is its scaffolding capabilities. Scaffolding allows you to create a boilerplate-style set of actions and templates that make it easy to manipulate data for a specific model. The scaffold provides methods and pages that allow you to insert, update, and delete records in your database. To scaffold the Event model, open the file app/controllers/events_controller.rb in your editor and add scaffold :event inside the class body. When you re finished, the file should look like Listing 3-4.
CHAPTER 3 GETTING SOMETHING RUNNING
Listing 3-4. The app/controllers/events_controller.rb File
class EventsController < ApplicationController scaffold :event end
That s all you need to generate a working scaffold of the Event model. Let s fire up the web server and test it. Start your local web server from the command line (./script/server) and browse to the events controller in your browser.
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