Rails Console: Creating Model Objects

We can create new records in the database by creating new model objects, setting their attributes, and saving them.

• We can create a new Post object by calling Post.new. We can create a new "Post" and assign it to a variable: post = Post.new
• You can see the object we got in the Rails console output. Notice that its attributes are all set to "nil": #<Post id: nil, title: nil, created_at: nil, updated_at: nil>
• You can set the attributes the same way you would on any other Ruby object. Let's assign a title for this new Post: post.title = "Hello, console!"
• To store it in the database, we need to call the "save" method on the object: post.save.
• We'll see an SQL query that inserts a new post into the "posts" table, with the "title" we assigned: INSERT INTO "posts" ("title", "created_at", "updated_at") VALUES (?, ?, ?) [["title", "Hello, console!"], ["created_at", 2016-07-13 19:50:08 UTC], ["updated_at", 2016-07-13 19:50:08 UTC]]

Every model object you save to the database gets a value written to its id database column. Notice that our Post object didn't have an id when we first created it.

• If we look at the Post after saving it, we'll see it's been assigned one: #<Post id: 7, title: "Hello, console!", created_at: "2016-07-13 19:50:08", updated_at: "2016-07-13 19:50:08">
• As we saw before, you can pass an object's id to the find method to look it back up later: Post.find(7)

Frequently Asked Questions

Q: In the console, I created a Post with Post.new, but when I type post.title = "some value" I get undefined local variable or method 'post'! What's going on?

A: Calling Post.new doesn't automatically assign it to a variable; the post variable doesn't exist until you assign a value to it. Be sure to assign the new Post to a variable with post = Post.new.