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Here we are, back on the rails logs
showing the processing of our request.

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This language generated by the post model.

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The model is responsible for storing and
retrieving data from users of your app.

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Model classes or Ruby classes
that usually, though not always,

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know how to read and
write data from a database.

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Those classes each have one or

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more attributes that hold data
you need to keep track of.

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So, if you were creating an airline
booking app, for example, you might have

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a flight model class with flight
number and departure time attributes.

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As well as a passenger model class,
with name and seat assignment attributes,

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among many others.

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You can create an instance of a model
class, set its attributes and then,

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call the Save method on it to write its
data to the database as a new record.

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Later on, you can call various methods to
retrieve those records from the database,

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each record gets returned as
a separate instance of the model class.

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So, here's how we're using the model
class to show a list of all

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posts in our blog app.

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The controller's index method has
the line @post equals Post.all.

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Post is the model class
representing this resource.

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Rails creates the source code for model
classes in the app models sub directory.

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Here's the post class in post.rb.

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Again, it doesn't look like much, but

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that's because post is a subclass
of the application record class.

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Prior to Rails 5, it would have been
a subclass of active record base, and

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in fact, it still is behind the scenes.

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The all method that
are controller calls and

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many other methods are inherited
from Application Record.

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The all method retrieves all of the post
objects stored in the database.

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It generates this query.

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This is in structured query language or
SQL,

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a language used to
communicate with databases.

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Rails generates SQL queries for you.

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This particular query loads the data from
all of the columns in all of the records

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in the post database table.

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Rails takes each database record, creates
an instance of the post Ruby class,

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and uses the database column values to
set the attributes of the post object,

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Post.all returns a collection of these
post objects which we then store in

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the posts instance variable.