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Creating a Model
3:32We want our /pages path to show a list of blog pages. But right now, our view template is just showing a static header. So let's set our controller up to load some Page data so that we can include it in our template.
We want our slash pages path to
show a list of blog pages but
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right now our view template is
just showing a static header.
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So let's set our controller
up to load some page data so
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that we can include it in our template.
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In our pages controller, we will limit the
index method to load a list of all pages
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and store it in an instance variable.
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So assign to an instance variable @pages.
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Notice that I named the instance
variable pages plural and
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not page singular since it's going to
hold a collection of multiple pages
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then we'll call the Page.all
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class method to load all page
records from the database.
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Let's save this and refresh our browser.
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We get an error
uninitialized constant page.
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Our controller is receiving
the user's request and
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attempting to load data from the model.
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But we haven't created
our page model class yet.
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It doesn't exist.
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So we get an error when we
attempt to reference it.
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So let's create a model class
now using Rails generator.
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Just as with scaffolds and controllers
rails has a generator for models.
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The model generator will create a source
file with the model class for us.
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At the same time it will create
a migration file that will set up
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a database table to hold records for
that model.
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Stop the server if it's running and
run the command bin/rails generate model,
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because we're generating a model class and
then the name of the model class page.
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Then just as with scaffolds we can specify
a series of attributes we want page
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objects to have along with the types of
database columns that should be created to
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hold that data we want pages to have title
and body attributes just like with posts.
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And then also a slug attribute that we
can use to make human readable URLs.
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So we'll add a title attribute and give
it a type of string with a title:string.
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Then we'll hit space and
add a body attribute.
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Page bodies are of course
much longer than titles so
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we'll give it a type of
text instead of string.
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Last we'll add a slug attribute
with a type of string again.
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Hit return to run the command and
it will create files with a model and
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a migration for us.
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The model classes in app models page.rb.
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As with the post model, it's not much
to look at because all its methods
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are inherited from ApplicationRecord.
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The migration is in a file
within the db migrate directory.
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It has commands to create a Pages table
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with all of the fields we specified on
the command line by default it also has
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a call to the timestamps method
which will set up created_at and
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updated_at columns that track when
a record was created or modified.
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It's not mentioned here but
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rails will automatically create
the all important ID column.
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That's used for
looking individual page records up later.
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We've created the migration, but
the database isn't updated yet.
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Remember we got a pending migration error
last time we created the migration without
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updating the database to avoid seeing
that next time we launch the server.
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We need to run bin/rails db:migrate,
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which will run the migration and
create the database table.
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Now let's run the server
again with bin/rails s.
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And then reload our browser.
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It will load successfully this time but
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no pages will be displayed.
We'll fix that next.
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