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User Model
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612 The Model File
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We ve seen how the User model generation in Listing 61 generated a migration file (Listing 62), and we saw in Figure 63 the results of running this migration: it updated a file called developmentsqlite3 by creating a table users with columns id, name, email, created_at, and updated_at Listing 61 also created the model itself; the rest of this section is dedicated to understanding it We begin by looking at the code for the User model, which lives in the file userrb inside the app/models/ directory; it is, to put it mildly, very compact (Listing 63)
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Listing 63 The brand new User model
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app/models/userrb
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class User < ActiveRecord::Base end
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Recall from Section 442 that the syntax class User < ActiveRecord::Base means that the User class inherits from ActiveRecord::Base, so that the User model automatically has all the functionality of the ActiveRecord::Base class Of course, knowledge of this inheritance doesn t do any good unless we know what ActiveRecord::Base contains, and we ll get a first taste starting momentarily Before we move on, though, there are two tasks to complete
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Model Annotation Though it s not strictly necessary, you might find it convenient to annotate your Rails models using the annotate-models gem (Listing 64)
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Listing 64 Adding the annotate-models gem to the Gemfile
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source 'http://rubygemsorg' group :development do gem 'rspec-rails', '201' gem 'annotate-models', '104' end group :test do end
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6: Modeling and Viewing Users, Part I
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(We place the annotate-models gem in a group :development block (analogous to group :test) because the annotations aren t needed in production applications) We next install it with bundle:
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$ bundle install
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This gives us a command called annotate, which simply adds comments containing the data model to the model file:
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$ annotate Annotated User
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The results appear in Listing 65
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Listing 65 The annotated User model
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app/models/userrb
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# == Schema Information # Schema version: <timestamp> # # Table name: users # # id :integer # name :string(255) # email :string(255) # created_at :datetime # updated_at :datetime # class User < ActiveRecord::Base end
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not null, primary key
I find that having the data model visible in the model files helps remind me which attributes the model has, but future code listings will usually omit the annotations for brevity
Accessible Attributes Another step that isn t strictly necessary but is a really good idea is to tell Rails which attributes of the model are accessible, ie, which attributes can be modified by out-
User Model
side users (such as users submitting requests with web browsers) We do this with the attr_accessible method (Listing 66) We ll see in 10 that using attr_accessible is important for preventing a mass assignment vulnerability, a distressingly common and often serious security hole in many Rails applications
Listing 66 Making the name and email attributes accessible
app/models/userrb
class User < ActiveRecord::Base attr_accessible :name, :email end
613 Creating User Objects
We ve done some good prep work, and now it s time to cash in and learn about Active Record by playing with our newly created User model As in 4, our tool of choice is the Rails console Since we don t (yet) want to make any changes to our database, we ll start the console in a sandbox:
$ rails console --sandbox Loading development environment in sandbox (Rails 301) Any modifications you make will be rolled back on exit >>
As indicated by the helpful message Any modifications you make will be rolled back on exit , when started in a sandbox the console will roll back (ie, undo) any database changes introduced during the session When working at the console, it s useful to keep an eye on the development log, which records the actual low-level SQL statements being issued by Active Record, as shown in Figure 64 The way to get this output at a Unix command line is to tail the log:
$ tail -f log/developmentlog
The -f flag ensures that tail will display additional lines as they are written I recommend keeping an open terminal window for tailing the log whenever working at the console