The Rails Guides: Views and Controllers

Question 1

How does the Controller handle requests in Rails?

Answer 1

The Controller orchestrates the handling of requests in Rails, typically delegating heavy code execution to the Model. It then manages the response generation process, handing off to the View when it’s time to send a response back to the user.

Question 2

What are the three ways to create an HTTP response from a controller in Rails?

Answer 2

From a controller, you can create an HTTP response by calling render to generate a full response, redirect_to to send a redirect status code, or head to create a response consisting solely of HTTP headers.

Question 3

Explain the concept of “convention over configuration” in the context of default rendering in Rails.

Answer 3

“Convention over configuration” in Rails means that controllers automatically render views with names corresponding to valid routes by default, reducing the need for explicit rendering calls.

Question 4

How does Rails automatically determine which view to render in a controller action?

Answer 4

Rails automatically renders a view with a name corresponding to the controller action unless explicitly specified otherwise. For example, the index action in the BooksController renders the index.html.erb view by default.

Question 5

What happens if you don’t explicitly call render at the end of a controller action in Rails?

Answer 5

If you don’t explicitly call render at the end of a controller action in Rails, Rails will automatically look for the corresponding view template based on the action name.

Question 6

What is the purpose of the render method in Rails controllers?

Answer 6

The render method in Rails controllers is used to render views, allowing controllers to generate content for use by a browser.

Question 7

How can you render the view corresponding to a different template within the same controller?

Answer 7

You can render the view corresponding to a different template within the same controller by using the render method with the name of the view.

Question 8

Can you render a template from an entirely different controller using the render method?

Answer 8

Yes, you can render a template from an entirely different controller using the render method by specifying the full path relative to app/views.

Question 9

What are some options available for customizing the behavior of the render method?

Answer 9

Some options available for customizing the behavior of the render method include specifying content type, layout, location, status, formats, and variants.

Question 10

What does the render :inline option do in Rails controllers?

Answer 10

The render :inline option in Rails controllers allows you to supply ERB directly as part of the method call.

Question 11

When would you use the render plain: option in Rails?

Answer 11

The render plain: option in Rails is used to send plain text back to the browser, useful for responding to Ajax or web service requests.

Question 12

How can you render an HTML string back to the browser in Rails?

Answer 12

You can render an HTML string back to the browser in Rails using the render html: option.

Question 13

What is the purpose of rendering JSON in Rails, and how is it achieved?

Answer 13

Rails supports rendering JSON responses for use by Ajax libraries. This is achieved using the render json: option.

Question 14

How does Rails support rendering XML responses?

Answer 14

Rails has built-in support for converting objects to XML and rendering that XML back to the caller using the render xml: option.

Question 15

Can you render vanilla JavaScript using Rails? If so, how?

Answer 15

Yes, Rails can render vanilla JavaScript using the render js: option.

Question 16

What does the render body: option do in Rails controllers?

Answer 16

The render body: option in Rails controllers sends a raw content back to the browser without setting any content type.

Question 17

How can you render a raw file in Rails from an absolute path?

Answer 17

You can render a raw file in Rails from an absolute path using the render file: option.

Question 18

What are the options available for specifying layouts in Rails?

Answer 18

Options available for specifying layouts in Rails include specifying layout files directly or deferring the choice of layout until runtime.

Question 19

How can you defer the choice of layout until a request is processed in Rails?

Answer 19

You can defer the choice of layout until a request is processed in Rails by using a symbol or an inline method like a Proc.

Question 20

What are conditional layouts in Rails, and how are they specified?

Answer 20

Conditional layouts in Rails are specified using the :only and :except options, which take method names corresponding to controller actions.

Question 21

How does layout inheritance work in Rails controllers?

Answer 21

Layout inheritance in Rails controllers means that layout declarations cascade downward in the hierarchy, and more specific layout declarations always override more general ones.

Question 22

How does template inheritance work in Rails controllers?

Answer 22

Template inheritance in Rails controllers means that if a template or partial is not found in the conventional path, the controller will look for a template or partial to render in its inheritance chain.

Question 23

What can cause “double render errors” in Rails, and how can they be avoided?

Answer 23

“Double render errors” in Rails are caused by having more than one call to render or redirect in a single code path. They can be avoided by ensuring there’s only one call to render or redirect per action, possibly using return to exit early from the action.

Question 24

What is the purpose of the redirect_to method in Rails?

Answer 24

The redirect_to method in Rails tells the browser to send a new request for a different URL.

Question 25

How does redirect_back differ from redirect_to in Rails?

Answer 25

redirect_back returns the user to the page they just came from by pulling the location from the HTTP_REFERER header, while redirect_to sends the browser to a specified URL.

Question 26

What happens to method execution after calling redirect_to or redirect_back in Rails?

Answer 26

Method execution continues after calling redirect_to or redirect_back in Rails. Statements occurring after them will be executed unless halted by an explicit return or some other halting mechanism.

Question 27

How can you specify a different HTTP status code when using redirect_to in Rails?

Answer 27

You can specify a different HTTP status code, such as 301 for a permanent redirect, by using the :status option with the redirect_to method.

Question 28

What misconception about redirect_to do inexperienced developers often have?

Answer 28

Inexperienced developers sometimes think of redirect_to as a “goto” command, moving execution from one place to another in Rails code. However, redirect_to actually stops the code execution and waits for a new request from the browser, sending back an HTTP 302 status code with the new request URL.

Question 29

How can you handle scenarios where a required variable is nil using redirect_to in Rails?

Answer 29

If a required variable is nil, you can use redirect_to to redirect to another action instead of rendering. This ensures that the browser makes a fresh request and the necessary variables are set up properly.

Question 30

What is the purpose of the head method in Rails?

Answer 30

The head method in Rails is used to send responses with only headers to the browser, allowing you to specify an HTTP status code and additional header options.

Question 31

How can you use the head method to return an error header in Rails?

Answer 31

You can use the head method with a specific status code, such as :bad_request, to return an error header to the browser in Rails.

Question 32

What are some scenarios where you might use partials in Rails views?

Answer 32

Partials in Rails views are useful for breaking down the rendering process into manageable chunks, reducing duplication, and organizing reusable pieces of code.

Question 33

How do you pass local variables to partials in Rails?

Answer 33

Local variables can be passed to partials in Rails using the locals option with the render method or by using the as option when rendering a collection.

Question 34

What is the main form helper in Rails, and how is it typically used?

Answer 34

The main form helper in Rails is form_with. When called without arguments, it generates a form tag that submits to the current page via POST method.

Question 35

How can you create a basic search form using form_with?

Answer 35

You can create a basic search form by specifying the URL and method (GET) with form_with, along with input fields for the search query and a submit button.

Question 36

What are some commonly used form elements provided by the form builder object in Rails?

Answer 36

Some commonly used form elements include text fields, checkboxes, radio buttons, text areas, hidden fields, password fields, number fields, date and time fields, and more.

Question 37

How are checkboxes and radio buttons generated using the form builder in Rails?

Answer 37

Checkboxes and radio buttons are generated using form.check_box and form.radio_button methods, respectively. They take the input name as the first parameter and optional label as the second parameter.

Question 38

How can you bind a form to a model object in Rails?

Answer 38

You can bind a form to a model object by specifying the model argument in form_with. This automatically populates form fields with values from the model and sets the form action to an appropriate route for the model.

Question 39

What is the significance of the _method parameter in Rails forms?

Answer 39

The _method parameter allows Rails to emulate HTTP methods other than GET and POST by overriding the actual method used for form submission. This is useful for making PATCH, PUT, and DELETE requests.

Question 40

How can you create a select box in Rails, and what are some advanced features it supports?

Answer 40

You can create a select box using the form.select method in Rails, which supports options like default selection, option groups, and binding to model attributes.

Question 41

How can you leverage time zone and country select functionalities in Rails forms?

Answer 41

To select time zones, you can use the time_zone_select helper, which generates options from a list of pre-defined time zones. For country selection, you can use the country_select plugin, which provides similar functionality.

Question 42

What are alternative options provided by Rails if HTML5 date and time inputs are not used?

Answer 42

Rails provides alternative date and time form helpers that render plain select boxes for each temporal component (e.g., year, month, day, etc).

Question 43

How does Rails handle the submission of form data when using select boxes for date and time inputs?

Answer 43

When the form is submitted, Rails assembles specially-named values (e.g., “birth_date(1i)”) into a full date or time based on the declared type of the model attribute. These values are then accessible via the params hash.

Question 44

What are the helpers provided by Rails for rendering select boxes for individual temporal components?

Answer 44

Rails provides helpers like select_year, select_month, select_day, select_hour, select_minute, and select_second for rendering select boxes for individual temporal components.

Question 45

How does the collection_select helper differ from the select helper in terms of specifying choices?

Answer 45

In collection_select, the value method is specified first followed by the text label method, which is opposite to the order used in the select helper.

Question 46

Explain the purpose of the accepts_nested_attributes_for method in Rails models.

Answer 46

The accepts_nested_attributes_for method in Rails models allows creating, updating, and optionally destroying associated records through the parent record’s form.

Question 47

What is the significance of the _destroy attribute in nested forms?

Answer 47

The _destroy attribute, when set to a truthy value (e.g., true), indicates that the associated record should be destroyed upon form submission, allowing users to remove associated objects.

Question 48

How can you prevent empty records from being created in nested forms?

Answer 48

You can use the :reject_if option with accepts_nested_attributes_for to specify a proc that determines whether to build an associated object based on the submitted attributes.

Question 49

What is the purpose of tag helpers like check_box_tag in Rails?

Answer 49

Tag helpers like check_box_tag are used to render form fields outside the context of a form builder, providing a convenient way to generate form elements.

Question 50

What is the role of a controller in the MVC architecture?

Answer 50

In the MVC architecture, a controller acts as the middleman between models and views. It receives requests, interacts with models to fetch or save data, and then uses views to generate appropriate output for the user.

Question 51

What is the naming convention recommended for controllers in Rails?

Answer 51

The naming convention suggests pluralization of the last word in the controller’s name. For example, “ClientsController” is preferred over “ClientController.”

Question 52

How does Rails determine which controller action to run for a given request?

Answer 52

Rails determines the controller action based on the routing. When a request is received, the routing system determines the appropriate controller and action to handle it.

Question 53

What types of parameters can be accessed in Rails controller actions?

Answer 53

Rails controller actions can access both query string parameters and POST data parameters. These parameters are available in the params hash in the controller.

Question 54

How can nested parameters be permitted in Rails controller strong parameters?

Answer 54

Nested parameters can be permitted by using the permit method with nested hashes or arrays. For example, params.permit(:name, { emails: [] }) permits the name attribute and an array of emails.

Question 55

What is the purpose of the session in a Rails application?

Answer 55

The session in a Rails application allows you to store small amounts of data persistently between requests for each user. It is commonly used for tasks like user authentication and passing error messages between requests.

Question 56

How can you access the session in a Rails controller?

Answer 56

You can access the session in a Rails controller through the session instance method. This allows you to read and write data to the session.

Question 57

What is the difference between flash and flash.now in Rails?

Answer 57

The flash hash stores data that is available to the next request, while flash.now stores data that is only available in the current request. This is useful for displaying error messages immediately after a failed action.

Question 58

What are cookies in Rails, and how are they accessed?

Answer 58

Cookies in Rails are small amounts of data stored on the client’s browser. They are accessed using the cookies method, which works similar to a hash.

Question 59

How can you auto-fill a form field with a stored cookie value in Rails?

Answer 59

To auto-fill a form field with a stored cookie value in Rails, you can use code similar to this:

Question 60

How can you delete a cookie in Rails?

Answer 60

To delete a cookie in Rails, you can use the cookies.delete(:key) method.

Question 61

What are signed and encrypted cookie jars in Rails, and how do they differ?

Answer 61

Signed cookie jars append a cryptographic signature on cookie values to protect integrity, while encrypted cookie jars encrypt the values in addition to signing them, preventing them from being read by the end-user.

Question 62

What is the default serializer for cookies in Rails, and what are its limitations?

Answer 62

The default serializer for cookies in Rails is :json. Its limitations include limited support for round-tripping Ruby objects, such as Date, Time, and Symbol objects, which will be serialized and deserialized into Strings.

Question 63

How can you set a cookie with an expiration date in Rails?

Answer 63

You can set a cookie with an expiration date in Rails using code similar to this:

Question 64

What are filters in Rails, and how do they work?

Answer 64

Filters in Rails are methods that are run “before”, “after”, or “around” a controller action. They are inherited, so if set on ApplicationController, they will be run on every controller in the application.

Question 65

How can you prevent a filter from running before specific actions in Rails?

Answer 65

You can prevent a filter from running before specific actions in Rails using the skip_before_action method, specifying the actions to skip the filter for.

Question 66

What are “after” and “around” filters in Rails, and how do they differ from “before” filters?

Answer 66

“After” filters are run after an action has been executed, while “around” filters can run before and after an action. They differ from “before” filters in terms of when they are executed in relation to the action.

Question 67

How can you use blocks directly with action methods in Rails?

Answer 67

You can use blocks directly with action methods in Rails by passing a block to the *_action methods. The block receives the controller as an argument.

Question 68

What is HTTP Basic Authentication in Rails, and how can you implement it?

Answer 68

HTTP Basic Authentication is an authentication scheme supported by most browsers. In Rails, you can implement it using the http_basic_authenticate_with method.

Question 69

How can you send a file to the user instead of rendering an HTML page in Rails?

Answer 69

You can send a file to the user instead of rendering an HTML page in Rails using the send_file method.

Question 70

What is the purpose of log filtering in Rails?

Answer 70

Log filtering in Rails is used to filter out sensitive information from log files, such as passwords or redirect URLs.

Question 71

How can you force communication to your controller to be only via HTTPS in Rails?

Answer 71

You can force communication to your controller to be only via HTTPS in Rails by enabling the ActionDispatch::SSL middleware via the config.force_ssl option in your environment configuration.

Question 72

What is the purpose of the built-in health check endpoint in Rails?

Answer 72

The purpose of the built-in health check endpoint in Rails is to provide a simple way to check if the application has booted successfully and is running without exceptions.

Question 73

What is the purpose of the Rails router?

Answer 73

The purpose of the Rails router is to recognize URLs and dispatch them to a controller’s action or to a Rack application. Additionally, it can generate paths and URLs, reducing the need to hardcode strings in views.

Question 74

How does the Rails router connect URLs to code?

Answer 74

When an incoming request is received, such as “GET /patients/17”, the Rails router matches it to a controller action based on the defined routes. For example, if the route is “get ‘/patients/:id’, to: ‘patients#show’”, the request is dispatched to the “show” action of the “patients” controller with the appropriate parameters.

Question 75

How does Rails generate paths and URLs from code?

Answer 75

Rails can generate paths and URLs by defining routes with specific names using the “as” option. For instance, if the route is “get ‘/patients/:id’, to: ‘patients#show’, as: ‘patient’”, and in the controller you have “@patient = Patient.find(params[:id])”, then in the view, you can use “patient_path(@patient)” to generate the path “/patients/17”.

Question 76

What configuration file contains the routes for a Rails application?

Answer 76

The routes for a Rails application are typically defined in the “config/routes.rb” file.

Question 77

What does resource routing in Rails allow you to do?

Answer 77

Resource routing in Rails allows you to quickly declare all common routes for a given resourceful controller, including index, show, new, edit, create, update, and destroy actions.

Question 78

How does Rails handle CRUD operations with resourceful routes?

Answer 78

In Rails, each resourceful route maps HTTP verbs and URLs to controller actions, corresponding to specific CRUD operations in a database. For example, the route “resources :photos” creates seven different routes mapping to the Photos controller for actions like index, show, create, update, and delete.

Question 79

What are some advantages of using path and URL helpers in Rails?

Answer 79

Using path and URL helpers in Rails reduces the brittleness of views and makes code easier to understand. It also helps avoid hardcoding URLs in views, which can lead to cleaner and more maintainable code.

Question 80

How can you add additional routes to a resource in Rails?

Answer 80

In Rails, you can add additional routes to a resource using member routes for actions that apply to individual members of the resource, or collection routes for actions that apply to the entire collection. These routes can be defined within a member or collection block in the resources declaration.

Question 81

How can you define defaults for routes in Rails?

Answer 81

Defaults for routes in Rails can be defined by supplying a hash for the :defaults option. For example:

Question 82

What are three examples of non-resourceful routes in Rails?

Answer 82

Non-resourceful routes in Rails provide flexibility for mapping arbitrary URLs to actions. Three examples include:
Bound Parameters: Mapping routes with optional parameters, such as photos(/:id) to photos#display.
Dynamic Segments: Defining routes with variable segments accessible in the action’s params, like photos/:id/:user_id to photos#show.
Static Segments: Specifying fixed segments in routes, such as photos/:id/with_user/:user_id to photos#show.

Question 83

How can you set up dynamic segments within a regular route?

Answer 83

Dynamic segments in a regular route can be set up by defining a route with variable segments. For example:

Incoming paths like /photos/1/2 will be dispatched to the show action of the PhotosController, with params[:id] as “1” and params[:user_id] as “2”.

Question 84

What is the purpose of using static segments in route creation?

Answer 84

Static segments in route creation serve to define fixed parts of a route without using dynamic parameters.

This route responds to paths like /photos/1/with_user/2, where params would be { controller: ‘photos’, action: ‘show’, id: ‘1’, user_id: ‘2’ }.