+ part: active record

Author: palkan

src/content/tutorial/4-database/2-database-migrations/content.md

@@ -1,6 +1,7 @@
 ---
 type: lesson
 title: Database Migrations
+focus: /workspace/store/db/migrate/20250521010850_create_products.rb
 custom:
   shell:
     workdir: "/workspace/store"
@@ -21,7 +22,7 @@ they can be deployed to production (live, online!) safely.
 
 In the editor, open the migration Rails created for us so we can see what
 the migration does. This is located in
-`db/migrate/<timestamp>_create_products.rb`:
+`db/migrate/20250521010850_create_products`:
 
 ```file:/workspace/store/db/migrate/20250521010850_create_products.rb
 ```

src/content/tutorial/4-database/3-running-migrations/content.md

@@ -1,6 +1,7 @@
 ---
 type: lesson
 title: Running Migrations
+focus: /workspace/store/db/migrate/20250521010850_create_products.rb
 custom:
   shell:
     workdir: "/workspace/store"
@@ -23,10 +24,10 @@ This command checks for any new migrations and applies them to your database.
 Its output looks like this:
 
 ```bash
-== 20240426151900 CreateProducts: migrating ===================================
+== 20250521010850 CreateProducts: migrating ===================================
 -- create_table(:products)
    -> 0.0030s
-== 20240426151900 CreateProducts: migrated (0.0031s) ==========================
+== 20250521010850 CreateProducts: migrated (0.0031s) ==========================
 ```
 
 :::tip

src/content/tutorial/5-console/1-rails-console/_files/.tk-config.json

@@ -1,3 +1,3 @@
 {
-  "extends": "../../../4-database/3-running-migrations/_files"
+  "extends": "../../../../../templates/create-products"
 }

src/content/tutorial/5-console/1-rails-console/content.md

@@ -4,9 +4,6 @@ title: Rails Console
 custom:
   shell:
     workdir: "/workspace/store"
-  fs:
-    remove:
-      - "/workspace/store"
 ---
 
 Rails Console

src/content/tutorial/6-active-record/1-intro/_files/.tk-config.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../../templates/create-products"
+}

src/content/tutorial/6-active-record/1-intro/_files/workspace/.keep

@@ -0,0 +1,48 @@
+---
+type: lesson
+title: Active Record Basics
+focus: /workspace/store/app/models/product.rb
+custom:
+  shell:
+    workdir: "/workspace/store"
+---
+
+Active Record Basics
+--------------------------
+
+When we ran the Rails model generator to create the `Product` model, it created
+a file at `app/models/product.rb`. This file creates a class that uses Active
+Record for interacting with our `products` database table.
+
+```ruby
+class Product < ApplicationRecord
+end
+```
+
+You might be surprised that there is no code in this class. How does Rails know
+what defines this model?
+
+When the `Product` model is used, Rails will query the database table for the
+column names and types and automatically generate code for these attributes.
+Rails saves us from writing this boilerplate code and instead takes care of it
+for us behind the scenes so we can focus on our application logic instead.
+
+Let's use the Rails console to see what columns Rails detects for the Product
+model.
+
+Run:
+
+```irb
+store(dev)> Product.column_names
+```
+
+And you should see:
+
+```irb
+=> ["id", "name", "created_at", "updated_at"]
+```
+
+Rails asked the database for column information above and used that information
+to define attributes on the `Product` class dynamically so you don't have to
+manually define each of them. This is one example of how Rails makes development
+a breeze.

src/content/tutorial/6-active-record/1-intro/content.md

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../../templates/create-products"
+}

src/content/tutorial/6-active-record/2-creating-records/_files/.tk-config.json

@@ -0,0 +1,53 @@
+---
+type: lesson
+title: Creating Records
+focus: /workspace/store/app/models/product.rb
+custom:
+  shell:
+    workdir: "/workspace/store"
+---
+
+### Creating Records
+
+We can instantiate a new Product record with the following code:
+
+```irb
+store(dev)> product = Product.new(name: "T-Shirt")
+=> #<Product:0x000000012e616c30 id: nil, name: "T-Shirt", created_at: nil, updated_at: nil>
+```
+
+The `product` variable is an instance of `Product`. It has not been saved to the
+database, and so does not have an ID, created_at, or updated_at timestamps.
+
+We can call `save` to write the record to the database.
+
+```irb
+store(dev)> product.save
+  TRANSACTION (0.1ms)  BEGIN immediate TRANSACTION /*application='Store'*/
+  Product Create (0.9ms)  INSERT INTO "products" ("name", "created_at", "updated_at") VALUES ('T-Shirt', '2024-11-09 16:35:01.117836', '2024-11-09 16:35:01.117836') RETURNING "id" /*application='Store'*/
+  TRANSACTION (0.9ms)  COMMIT TRANSACTION /*application='Store'*/
+=> true
+```
+
+When `save` is called, Rails takes the attributes in memory and generates an
+`INSERT` SQL query to insert this record into the database.
+
+Rails also updates the object in memory with the database record `id` along with
+the `created_at` and `updated_at` timestamps. We can see that by printing out
+the `product` variable.
+
+```irb
+store(dev)> product
+=> #<Product:0x00000001221f6260 id: 1, name: "T-Shirt", created_at: "2024-11-09 16:35:01.117836000 +0000", updated_at: "2024-11-09 16:35:01.117836000 +0000">
+```
+
+Similar to `save`, we can use `create` to instantiate and save an Active Record
+object in a single call.
+
+```irb
+store(dev)> Product.create(name: "Pants")
+  TRANSACTION (0.1ms)  BEGIN immediate TRANSACTION /*application='Store'*/
+  Product Create (0.4ms)  INSERT INTO "products" ("name", "created_at", "updated_at") VALUES ('Pants', '2024-11-09 16:36:01.856751', '2024-11-09 16:36:01.856751') RETURNING "id" /*application='Store'*/
+  TRANSACTION (0.1ms)  COMMIT TRANSACTION /*application='Store'*/
+=> #<Product:0x0000000120485c80 id: 2, name: "Pants", created_at: "2024-11-09 16:36:01.856751000 +0000", updated_at: "2024-11-09 16:36:01.856751000 +0000">
+```