Partial templates in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to render a partial named '_menu.html.erb' inside a view.

Ruby on Rails

<%= render [1] %>

Drag options to blanks, or click blank then click option'

Apartial: 'menu'

B'menu'

Ctemplate: 'menu'

Dpartial: :menu

Attempts:

3 left

💡 Hint

Common Mistakes

Including the underscore in the partial name.

Using 'partial:' keyword incorrectly.

Using symbols instead of strings.

In Rails, to render a partial named '_menu.html.erb', you use render 'menu'. This tells Rails to look for the partial with that name.

2fill in blank

medium

Complete the code to render a partial named '_item.html.erb' and pass a local variable 'product' to it.

Ruby on Rails

<%= render partial: 'item', locals: [1] %>

Drag options to blanks, or click blank then click option'

A{ product: @product }

B{ product => @product }

Cproduct: @product

Dproduct = @product

Attempts:

3 left

💡 Hint

Common Mistakes

Using => instead of : inside the hash.

Not wrapping the locals in curly braces.

Using assignment (=) instead of hash syntax.

To pass local variables to a partial, you use the locals option with a hash. The key is the variable name inside the partial, and the value is the data you pass.

3fill in blank

hard

Fix the error in rendering a collection of @products with the partial '_product.html.erb'.

Ruby on Rails

<%= render [1] %>

Drag options to blanks, or click blank then click option'

Apartial: 'product', collection: @products

Bpartial: @products

Ccollection: @products

Dpartial: 'products', collection: @product

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural partial name.

Passing collection without partial.

Mixing singular and plural variable names.

To render a collection of objects with a partial, use render partial: 'product', collection: @products. This renders the partial for each item in the collection.

4fill in blank

hard

Fill both blanks to render a partial '_comment.html.erb' for each comment in @comments and pass each comment as a local variable named 'comment'.

Ruby on Rails

<%= render partial: [1], collection: [2], locals: { comment: comment } %>

Drag options to blanks, or click blank then click option'

A'comment'

B@comments

C'comments'

D@comment

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural partial name.

Passing a single comment instead of the collection.

Not matching local variable name with partial.

The partial name should be singular 'comment' and the collection is the array @comments. This renders the partial for each comment and passes it as a local variable.

5fill in blank

hard

Fill all three blanks to render a partial '_user.html.erb' for each user in @users, pass each user as 'user', and add a spacer partial '_spacer.html.erb' between each user.

Ruby on Rails

<%= render partial: [1], collection: [2], locals: { user: user }, [3]: 'spacer' %>

Drag options to blanks, or click blank then click option'

A'user'

B@users

Cspacer_template

Dspacer_template_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong key for spacer partial.

Using plural partial name.

Not passing the local variable correctly.

Use partial: 'user' for the user partial, collection: @users for the list, and spacer_template: 'spacer' to add the spacer partial between items.

Practice

1. What is the main purpose of using partial templates in Rails views?

easy

A. To define routes for the application

B. To speed up database queries

C. To handle user authentication

D. To reuse small pieces of view code across different pages

Solution

1. Step 1: Understand what partial templates are

   Partial templates are small view files that can be included in other views to avoid repeating code.

2. Step 2: Identify the main use case

   The main use is to reuse small pieces of view code across different pages, improving maintainability.

3. Final Answer:

   To reuse small pieces of view code across different pages -> Option D

4. Quick Check:

   Partial templates = reuse view code [OK]

Hint: Partial templates reuse view parts, not logic or routes [OK]

Common Mistakes:

• Thinking partials speed up database queries
• Confusing partials with authentication logic
• Assuming partials define routes

2. Which of the following is the correct syntax to render a partial named _menu.html.erb in a Rails view?

easy

A. <%= partial 'menu' %>

B. <%= render 'menu' %>

C. <%= include 'menu' %>

D. <%= render_partial 'menu' %>

Solution

1. Step 1: Recall the Rails partial rendering syntax

   Rails uses render 'partial_name' to include partials, omitting the underscore and file extension.

2. Step 2: Match the correct syntax

   The correct syntax is <%= render 'menu' %> to render _menu.html.erb.

3. Final Answer:

   <%= render 'menu' %> -> Option B

4. Quick Check:

   Render partial = render 'name' [OK]

Hint: Use render 'partial_name' without underscore or extension [OK]

Common Mistakes:

• Using 'partial' instead of 'render'
• Using 'include' which is not a Rails helper
• Adding underscore in render argument

3. Given the following code in a Rails view:

<%= render partial: 'product', collection: @products, as: :item %>

What will be the local variable name inside the _product.html.erb partial for each item?

medium

A. item

B. product

C. @products

D. collection

Solution

1. Step 1: Understand collection rendering with 'as'

   When rendering a collection with render partial: 'name', collection: ..., as: :var, each element is passed as var inside the partial.

2. Step 2: Identify the local variable name

   Here, as: :item means inside _product.html.erb each element is accessible as item.

3. Final Answer:

   item -> Option A

4. Quick Check:

   Collection with 'as' sets local variable name [OK]

Hint: Use 'as' option to rename local variable in collection partial [OK]

Common Mistakes:

• Assuming default variable name 'product' instead of 'item'
• Using instance variable '@products' inside partial
• Confusing 'collection' as variable name

4. What is wrong with this code snippet in a Rails view?

<%= render 'user', user: @user %>

Assuming the partial is named _user.html.erb and expects a local variable user.

medium

A. The syntax should be render partial: 'user', locals: { user: @user }

B. The partial name should include the underscore: render '_user'

C. The code is correct and will work as expected

D. You cannot pass local variables to partials

Solution

1. Step 1: Check the shorthand syntax for passing locals

   Rails allows passing locals directly by naming the variable in the render call, like render 'user', user: @user.

2. Step 2: Confirm partial naming rules

   The underscore is omitted in the render call; Rails finds _user.html.erb automatically.

3. Final Answer:

   The code is correct and will work as expected -> Option C

4. Quick Check:

   Passing locals shorthand is valid [OK]

Hint: Passing locals as named args in render is valid shorthand [OK]

Common Mistakes:

• Thinking underscore is required in render argument
• Believing locals must be inside a hash named 'locals'
• Assuming locals cannot be passed at all

5. You want to render a list of comments using a partial _comment.html.erb. Each comment should be passed as comment local variable. Which is the best way to do this in Rails?

hard

A. <%= render partial: 'comment', collection: @comments %>

B. <%= render 'comment', comments: @comments %>

C. <%= render partial: 'comment', collection: @comments, as: :comments %>

D. <%= render partial: 'comment', locals: { comment: @comments } %>

Solution

1. Step 1: Understand collection rendering default variable

   When rendering a collection with render partial: 'comment', collection: @comments, Rails passes each element as comment by default (partial name without underscore).

2. Step 2: Evaluate other options

   <%= render 'comment', comments: @comments %> passes the whole array as a single local, not each comment. <%= render partial: 'comment', collection: @comments, as: :comments %> passes each as comments (plural). <%= render partial: 'comment', locals: { comment: @comments } %> passes the entire array as one variable, not individual comments.

3. Final Answer:

   <%= render partial: 'comment', collection: @comments %> -> Option A

4. Quick Check:

   Collection rendering uses partial name as local by default [OK]

Hint: Render collection with partial name to get default local variable [OK]

Common Mistakes:

• Passing whole array as one local variable
• Using 'as: :comments' which sets plural local name
• Confusing locals hash with collection rendering