`<%= render partial: "nav", selected: "about"}%>`

`<%= render partial: "nav", local_variables: {selected: "about"} %>`

`<%= render partial: "nav", locals: {selected: "about"}`

The `form_tag` method is for basic forms, while the `form_for` method is for multipart forms that include file uploads.

The `form_tag` method is for HTTP requests, while the `form_for` method is for AJAX requests.

The `form_tag` method typically expects a URL as its first argument, while the `form_for` method typically expects a model object.

The `form_tag` method is evaluated at runtime, while the `form_for` method is precompiled and cached.

A trigger that is executed before an alteration of an object's state

A method that is executed before an ActiveRecord model is saved

A callback that fires before an event is handled

A method in a controller that is executed before the controller action method

`match 'items', to 'items#update', via: [:put, :patch]`

INDEX, SHOW, NEW, CREATE, EDIT, UPDATE, DESTROY

It would include columns for `:documentable_id` and `:documentable_type`.

It would include columns for `:documentable` and `:type`.

It would include a column for `:polymorphic_type`.

Yes, any instance variables that are set in an action method on a controller can be accessed and displayed in a view.

Yes, instance variables set within an action method are accessible within a view, but only when render is explicitly called inside the action method.

No, instance variables in a controller are private and are not accessible.

No, instance variables can never be set in a controller action method.

`<select name="product_id"> <%= @products.each do |product| %> <option value="<%= product.id %>"/> <% end %></select>`

`<%= collection_select(:product, :product_id, Product.all, :id, :name) %>`

`errors(model, :address) << "This address is invalid"`

`display_error_for(model, :address, "This address is invalid")`

`model.errors[:address] << "This address is invalid"` [Reference: Custom Validator](https://guides.rubyonrails.org/v5.2/active_record_validations.html#custom-validators)

If sent using the PATCH HTTP method, the URL could be used to update a product in the database.

If sent using the POST HTTP method, the URL would create a new product in the database.

If sent using the GET HTTP method, the URL would execute the show action in ProductsController.

If sent using the DELETE HTTP method, the URL would call the destroy action by default.

The index action will run normally because `:index` is not listed as an argument to `before_action`.

The `require_login` method will automatically log in the user before running the index action.

The index action will not be run if the `require_login` method calls render or `redirect_to`.

`render partial: ‘shared/menu’, cached: true`

`render_with_cache partial: ‘shared/menu’`

`render partial: ‘shared/menu’, cached_with_variables: {}`

Concerns allow modularity and code reuse in models, controllers, and other classes.

Concerns are used to separate class methods from models.

Concerns are used to increase security of Rails applications.

Concerns are used to refactor Rails views.

`create` [Reference](https://medium.com/@de.usmanusa/difference-between-create-new-and-save-methods-in-activerecord-ea135085a08c)

`CoffeeOrder` [Reference](https://guides.rubyonrails.org/active_record_basics.html#naming-conventions)

The `has_many: through` association is the one-to-many equivalent to the `belongs_to` one-to-one association.

Both associations are identical, and `has_many: through` is maintained only for legacy purposes.

The `has_many` association is a one-to-many association, while `has_many: through` is a one-to-one association that matches through a third model.

Both are one-to-many associations but with `has_many :through`, the declaring model can associate through a third model.

Create an embedded Ruby file (.html.erb) and surround the Ruby code with `<% %>`.

Insert Ruby code inside standard HTML files and surround it with `<% %>`. The web server will handle the rest.

Create an embedded Ruby file (.html.erb) and surround the Ruby code with `<%= %>`.

Put the code in an .rb file and include it in a `<link>` tag of an HTML file.

`<% render 'view', use_layout: 'mobile' %>`

`<% render 'view', layout: 'mobile' %>` [Reference](https://stackoverflow.com/a/19277971)

`<% render_with_layout 'view', 'mobile' %>`

The product will not be updated and the edit template will be rendered.

The product will not be updated and the controller will raise an ActiveModel::ForbiddenAttributes exception.

The product will be updated with the values for name, style, and color, but the value for price will be ignored.

The product will be updated with the values for name, style, color, and price.

app/assets [Reference: RoR folder structure](https://images.app.goo.gl/CfKZPEQcGExfSx5C6)

MemCacheStore, MongoDBStore, MemoryStore, and FileStore

MemoryStore, FileStore, and CacheCacheStore

MemoryStore, FileStore, MemCacheStore, RedisCacheStore, and NullStore

MemoryStore, FileStore, MySQLStore, and RedisCacheStore

`rails generate controller --options {name: "Products", actions: "index"}`

`rails generate controller --name Products --action index`

`rails generate controller Products index`

`rails generate ProductsController --actions index`

Haml [Reference](https://medium.com/@bretcameron/so-you-think-you-know-html-7813c03f8ff6)

The method executes using "sudo" privileges.

Any ending line return will be omitted from the result.

The method will ignore exceptions that occur during execution.

It is a more powerful or destructive version of the method.

`csrf_meta_tags` [Reference] (https://api.rubyonrails.org/classes/ActionView/Helpers/CsrfHelper.html)

None of these callbacks will be called when `is_admin` is true.

It filters out submitted form parameters that are not named `:name` or `:sku` to make forms more secure.

It raises an error if parameters that are not named `:name` or `:sku` are found.

It raises an error if the `:name` and `:sku` parameters are set to `nil`.

The string assigned to flash[:notice] will not be available until the next browser request.

An instance variable should be used for flash[:notice]

This is an invalid syntax to use to assign valuse to flash[:notice]

The previous value of flash[:notice] will not be cleared automatically

Each database column requres adding a matching attr_accessor declaration in the ActiveRecord model.

All attributes in an ActiveRecord model are read-only declared as writable using attr_accessible

An instance of an ActiveRecord model will have attributes that match the columns in a corresponding database table.

ActiveRecord models can have only attributes that have a matching database column