WORKING WITH A DATABASE: ACTIVE RECORD in Font

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>> article.published_at = '2010-02-27' => "2010-02-27"

NOTE A return of nil always represents nothing. It s a helpful little object that stands in the place of nothingness. If you ask an object for something and it returns false, then false is something, so it s not a helpful representation. As a nerdy fact, in logics, false and true are equal and opposite values, but they re values in the end. The same is true of zero (0). The number 0 isn t truly nothing it s an actual representation of an abstract nothing, but it s still something. That s why in programming you have nil (or null in other languages).

Now, when you inspect your Article object, you can see that it has attributes: >> article => #<Article id: nil, title: "RailsConf", body: "RailsConf is the official gathering for Rails devel...", published_at: "2010-02-27 00:00:00", created_at: nil, updated_at: nil, excerpt: nil, location: nil> You still haven t written a new record. If you were to look at the articles table in the database, you wouldn t find a record for the object you re working with. (If you squint really hard at the preceding object-inspection string, notice that no id has been assigned yet.) That s because you haven t yet saved the object to the database. Fortunately, saving an Active Record object couldn t be any easier: >> article.save => true When you save a new record, a SQL INSERT statement is constructed behind the scenes. If the INSERT is successful, the save operation returns true; if it fails, save returns false. You can ask for a count of the number of rows in the table just to be sure that a record was created: >> Article.count => 1 Sure enough, you have a new article! You ve got to admit, that was pretty easy. (You may have created some articles during the scaffolding session. If so, don t be surprised if you have more than one article already.) Additionally, if you ask the article whether it s a new_record , it responds with false. Because it s saved, it s not new anymore: >> article.new_record => false Let s create another article. This time, omit all the chatter from the console so you can get a better sense of how the process plays out. You create a new object and place it in a variable, you set the object s attributes, and finally you save the record. Note that although you re using the local variable article to hold your object, it can be anything you want. Usually, you use a variable that indicates the type of object you re creating, like article or, if you prefer shorthand, just a:

>> article = Article.new >> article.title = "Introduction to SQL" >> article.body = "SQL stands for Structured Query Language, .." >> article.published_at = Date.today >> article.save

NOTE Although writer methods look like assignments, they re really methods in disguise. article.title =

'something' is the functional equivalent of article.title=('something'), where title=() is the method.

Now you re rolling! You ve already created a few articles and haven t had to write a lick of SQL. Given how easy this is, you may be surprised that you can do it in even fewer steps, but you can. Instead of setting each attribute on its own line, you can pass all of them to new at once. Here s how you can rewrite the preceding process of creating a new record in fewer lines of code: >> article = Article.new(:title => "Introduction to Active Record", :body => "Active Record is Rails's default ORM..", :published_at => Date.today) >> article.save Not bad, but you can do even better. The new constructor creates a new object, but it s your responsibility to save it. If you forget to save the object, it will never be written to the database.