ViewComponent (v4.0.0.rc5)

A framework for creating reusable, testable & encapsulated view components, built to integrate seamlessly with Ruby on Rails.

As of version 4, ViewComponent is in Long-Term Support and considered feature-complete.

What’s a ViewComponent?

ViewComponents are Ruby objects used to build markup. Think of them as an evolution of the presenter pattern, inspired by React.

ViewComponents are objects that encapsulate a template:

# app/components/message_component.rb
class MessageComponent < ViewComponent::Base
  def initialize(name:)
    @name = name
  end
end

<%# app/components/message_component.html.erb %>
<h1>Hello, <%= @name %>!<h1>

Which is rendered by calling:

<%# app/views/demo/index.html.erb %>
<%= render(MessageComponent.new(name: "World")) %>

Returning:

<h1>Hello, World!</h1>

Why use ViewComponents?

TL;DR

ViewComponents work best for templates that are reused or benefit from being tested directly. Partials and templates with significant amounts of embedded Ruby often make good ViewComponents.

Single responsibility

Rails applications often scatter view-related logic across models, controllers, and helpers, diluting their intended responsibilities. ViewComponents consolidate the logic needed for a template into a single class, resulting in a cohesive object that is easy to understand.

ViewComponent methods are implemented within the scope of the template, encapsulating them in proper object-oriented fashion. This cohesion is especially evident when multiple methods are needed for a single view.

Testing

ViewComponent was designed with the intention that all components should be unit tested. In the GitHub codebase, ViewComponent unit tests are over 100x faster than similar controller tests.

With ViewComponent, integration tests can be reserved for end-to-end assertions, with permutations covered at the unit level.

For example, to test the MessageComponent above:

class MessageComponentTest < GitHub::TestCase
  include ViewComponent::TestHelpers

  test "renders message" do
    render_inline(MessageComponent.new(name: "World"))

    assert_selector "h1", text: "Hello, World!"
  end
end

ViewComponent unit tests leverage the Capybara matchers library, allowing for complex assertions traditionally reserved for controller and browser tests.

Data Flow

Traditional Rails templates have an implicit interface, making it hard to reason about their dependencies. This can lead to subtle bugs when rendering the same template in different contexts.

ViewComponents use a standard Ruby initializer that clearly defines what’s needed to render, making reuse easier and safer than partials.

Performance

Based on several benchmarks, ViewComponents are ~2.5x faster than partials:

Comparison:
  component:     6498.1 i/s
    partial:     2676.5 i/s - 2.50x  slower

Code quality

Template code often fails basic Ruby standards: long methods, deep conditional nesting, and mystery guests abound.

ViewComponents are Ruby objects, making it easy to follow (and enforce) code quality standards.

Contributors

Hundreds of people have contributed to ViewComponent, including:

adillari adrianthedev aduth agrobbin allan-pires allmarkedup alvincrespo amhol andrewjtait andrewmcodes andreyazimov asgerb avinoth ayushn21 bankair baygeldin bdewater being-frank berniechiu betogrun bigbigdoudou biow0lf blakewilliams boardfish bobermod bobmaerten boof bpo bradparker brittanyellich brushbox bryanbeshore btrewern buraga-dmitrii caifara camertron carpenterjoseph ceritium cheshire137 chloe-meister claudiob cllns compostbrain cover crookedgrin cyupa czj danceparty dani-sc danieldiekmeier danielnc danielvdao dark-panda davekaro dbackeus dependabot[bot] dixpac dkniffin dlinch donapieppo dpaola2 drbragg dukex dvisockas dylanatsmith dylnclrk edwinthinks eebs eelcoj eileencodes elalemanyo elct9620 eleetyson elia enriikke erinnachen fbraure foca franco franzliedke fsateler fugufish fwolfst g13ydson github-actions[bot] gonzric1 grekko guillaumebriday hachi8833 halo henrikbjorn hirurg103 hjhart horacio horiaradu hparker htcarr3 igor-drozdov ihollander jacob-carlborg-apoex janklimo jaredcwhite jaredplanter javierav javierm jcoyne jdelstrother jdennes jess joelhawksley jogetblock johannesengl jonrohan jonspalmer jordanbrock joshmgross joshuaclayton jpbalarini juanmanuelramallo jwshuff jyunderwood kalashnikovisme kanejamison kaoru kaspermeyer keithamus kengos kenyonj khiga8 konnorrogers krazylegz kulturbande kylefox kzkn le0pard leighhalliday lfalcao llenk luccastera lxxxvi lyams mamhoff manuelpuyol marckohlbrugge marcoroth matheuspolicamilo matheusrich matt-yorkley mattbearman mattbrictson matthewlehner mattwr18 maxbeizer mbuckley mec meganemura mellowfish meneerprins metade mhw michaelem mikemcquaid mikepmunroe milk1000cc mitchellhenke mixergtz mkanakana mkdynamic moekiorg mrjonesbot mrloop mrrooijen mvz mxriverlynn myabc nachiket87 nashby natashau ncsmith24 neanias nickcoyne nickmalcolm nicolas-besnard nicolas-brousse nielsslot nitsas nshki olleolleolle ollie-nye otorain ozydingo p8 pacmakaveli palkan patrickarnett paul paulohenrique-gh pbstriker38 percyhanna petergoldstein peteryates phacks phil-janeapp porbas positivecontrol pouretrebelle progapandist rainerborene rdavid1099 rdkulp reedrolemodel reeganviljoen ricardotrindade richardmarbach rickychilcott rmacklin romaricpascal rubensmit rylanb ryogift sahglie salazarjosh sammyhenningsson sampart seanpdoyle sebastjanprachovskij sethherr sfnelson simonrand skryukov smashwilson sn3p spdawson spone srt32 steveclarke stiig sunny svetlins swanson talltorp talum tastypi tclem tdak tgaff thomascchen thutterer tkowalewski tmaier tmbv93 tmecklem tomasc tonkpils traels triskweline tysongach ultrawebmarketing varyform vinistock vsppedro wakematta websebdev willcosgrove wooly xkraty xronos-i-am xtr3me yakschuss yhirano55 yjukaku yshmarov yykamei zaratan zeneixe zspencer

Who uses ViewComponent?

Using ViewComponent? Send a pull request to update this list! You can also check out how various projects use ViewComponent.

Getting started →