c# barcode generator wpf ADVANCED ACTIVE RECORD: ENHANCING YOUR MODELS in Font

Creator PDF417 in Font ADVANCED ACTIVE RECORD: ENHANCING YOUR MODELS

ADVANCED ACTIVE RECORD: ENHANCING YOUR MODELS
Paint PDF417 In None
Using Barcode encoder for Font Control to generate, create PDF-417 2d barcode image in Font applications.
www.OnBarcode.com
Generating UPC-A In None
Using Barcode printer for Font Control to generate, create GS1 - 12 image in Font applications.
www.OnBarcode.com
def self.down drop_table :articles_categories end end You use the references method in the create_table block instead of using integer. It s just another notation that uses the association name as parameter instead of a field name; so, t.references :article is the same as t.integer :article_id. Feel free to pick the syntax you prefer. Go ahead and run the migrations: $ rake db:migrate == CreateCategories: migrating ===============================================
Printing DataMatrix In None
Using Barcode drawer for Font Control to generate, create DataMatrix image in Font applications.
www.OnBarcode.com
GS1 128 Encoder In None
Using Barcode creation for Font Control to generate, create EAN128 image in Font applications.
www.OnBarcode.com
-- create_table(:categories) -> 0.0032s == CreateCategories: migrated (0.0034s) ======================================
Draw GTIN - 13 In None
Using Barcode printer for Font Control to generate, create EAN13 image in Font applications.
www.OnBarcode.com
QR Code JIS X 0510 Printer In None
Using Barcode drawer for Font Control to generate, create QR-Code image in Font applications.
www.OnBarcode.com
CreateArticlesCategories: migrating =======================================
Barcode Maker In None
Using Barcode generation for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
Codabar Drawer In None
Using Barcode drawer for Font Control to generate, create ANSI/AIM Codabar image in Font applications.
www.OnBarcode.com
-- create_table(:articles_categories, {:id=>false}) -> 0.0011s == CreateArticlesCategories: migrated (0.0013s) ==============================
PDF417 Generator In Visual Basic .NET
Using Barcode generator for Visual Studio .NET Control to generate, create PDF417 image in VS .NET applications.
www.OnBarcode.com
PDF417 Encoder In None
Using Barcode generator for Online Control to generate, create PDF417 image in Online applications.
www.OnBarcode.com
With the Category model and the join table in place, you re ready to let Active Record in on your association. Open the Article and Category models, and add the has_and_belongs_to_many declarations to them, as shown in Listings 5-13 and 5-14. Listing 5-13. has_and_belongs_to_many Declaration in app/models/article.rb: http://gist.github.com/324055 class Article < ActiveRecord::Base validates :title, :presence => true validates :body, :presence => true belongs_to :user has_and_belongs_to_many :categories def long_title "#{title} - #{published_at}" end end
Code 128A Printer In VS .NET
Using Barcode encoder for VS .NET Control to generate, create Code 128 Code Set A image in .NET applications.
www.OnBarcode.com
Code 3 Of 9 Drawer In C#.NET
Using Barcode generation for Visual Studio .NET Control to generate, create Code-39 image in .NET framework applications.
www.OnBarcode.com
ADVANCED ACTIVE RECORD: ENHANCING YOUR MODELS
Create UCC - 12 In Objective-C
Using Barcode generator for iPad Control to generate, create UCC.EAN - 128 image in iPad applications.
www.OnBarcode.com
Print DataMatrix In None
Using Barcode generator for Software Control to generate, create Data Matrix image in Software applications.
www.OnBarcode.com
Listing 5-14. has_and_belongs_to_many Declaration in app/models/category.rb: http://gist.github.com/324057 class Category < ActiveRecord::Base has_and_belongs_to_many :articles end
Draw QR-Code In VB.NET
Using Barcode printer for .NET framework Control to generate, create QR Code image in VS .NET applications.
www.OnBarcode.com
Paint EAN 13 In None
Using Barcode creator for Microsoft Word Control to generate, create UPC - 13 image in Microsoft Word applications.
www.OnBarcode.com
Seeding Data
Generating EAN13 In Java
Using Barcode creator for Java Control to generate, create EAN-13 Supplement 5 image in Java applications.
www.OnBarcode.com
Create 1D In .NET Framework
Using Barcode generation for Visual Studio .NET Control to generate, create 1D image in .NET framework applications.
www.OnBarcode.com
As part of creating an application skeleton, Rails added a file called db/seeds.rb , which defines some data you always need in your database. The seeds file contains Ruby code, so you can use the classes and methods including associations available in your models, such as create and update. Open it and create one user and a few categories so that it looks like Listing 5-15. Listing 5-15. The db/seeds.rb File: http://gist.github.com/324072 user = User.create :email => 'mary@example.com', :password => 'guessit' Category.create [{:name => 'Programming'}, {:name => 'Event'}, {:name => 'Travel'}, {:name => 'Music'}, {:name => 'TV'}] That should do nicely. You can load your seed data using the Rake task db:seed: $ rake db:seed If you need to add more default categories later, you can append them to the seed file and reload it. If you want to rerun the seed data, the trick is that the seeds file doesn t know whether the records already in the database have to be cleaned up; running rake db:seed again adds all records one more time, and you end up with duplicate user and categories. You should instead call rake db:setup, which re-creates the database and adds the seed data as you may expect. You can also use fixtures to perform this same task of loading sample data for your application. Fixtures are a textual representation of database records, used for testing. 10 talks more about fixtures. Let s give this a test run. Get your console ready, reload!, and run the following commands: >> => >> => >> => >> => >> => article = Article.last #<Article id: 8, title: "Associations", > category = Category.find_by_name('Programming') #<Category id: 1, name: "Programming", ..> article.categories << category [#<Category id: 1, name: "Programming", ..>] article.categories.any true article.categories.size 1
Painting Matrix Barcode In .NET
Using Barcode creation for ASP.NET Control to generate, create 2D Barcode image in ASP.NET applications.
www.OnBarcode.com
Encode Barcode In Java
Using Barcode creator for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
ADVANCED ACTIVE RECORD: ENHANCING YOUR MODELS
Here, you automatically associate a category with an article using the << operator. You can even do this from the category s side of the association. Try the following: >> => >> => >> => category.articles.empty false category.articles.size 1 category.articles.first.title "Associations"
You just did the opposite of the previous test. has_and_belongs_to_many works in both directions, right So, you found your category and asked it for its first article titled Associations , because that s what you associated in the other direction, too. Using has_and_belongs_to_many is a very simple way to approach many-to-many associations. However, it has its limitations. Before you re tempted to use it for more than associating categories with articles, note that it has no way of storing additional information on the join. What if you want to know when or why someone assigns a category to an article This kind of data fits naturally in the join table. Rails includes another type of association called has_many :through, which allows you to create rich joins like this.
Copyright © OnBarcode.com . All rights reserved.