Rails%203%20In%20Action

First steps
vides an environment for you to experiment with Ruby without having to create new
files. The console prompt looks like this:
Loading development environment (Rails 3.1.0.beta)
irb(main):001:0>
At this prompt, 12 you can enter any valid Ruby and it’ll be evaluated. But for now, the
purpose of opening this console is to test the newly appointed validation. To do this,
try to create a new project record by calling the create method. The create method
is similar to the new method, but it attempts to create an object and then a database
record for it rather than just the object. You use it identically to the new method:
irb(main):001:0> Project.create
=> #
Here you get a new Project object with the name attribute set to nil, as you should
expect because you didn’t specify it. The id attribute is nil too, which indicates that
this object is not persisted (saved) in the database.
If you comment out or remove the validation from inside the Project class and
type reload! in your console, the changes you just made to the model are reloaded.
When the validation is removed, you have a slightly different outcome when you call
Project.create:
irb(main):001:0> Project.create
=> #
Here, the name field is still expectedly nil, but the other three attributes have values.
Why? When you call create on the Project model, Rails builds a new Project object
with any attributes you pass it 13 and checks to see if that object is valid. If it is, Rails sets
the created_at and updated_at attributes to the current time and then saves it to the
database. After it’s saved, the id is returned from the database and set on your object.
This object is valid, according to Rails, because you removed the validation, and therefore
Rails goes through the entire process of saving.
The create method has a bigger, meaner brother called create! (pronounced create
BANG!). Re-add or uncomment the validation from the model and type reload! in
the console, and you’ll see what this mean variant does with this line:
irb(main):001:0> Project.create!
ActiveRecord::RecordInvalid: Validation failed: Name can't be blank
12 Although you may see something similar to ruby-1.9.2-p180 :001 > too, which is fine.
13 The first argument for this method is the attributes. If there is no argument passed, then all attributes default
to their default values.
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