| name | vanilla-rails-views |
| description | Use when writing ERB templates, partials, or view helpers - covers partial organization, optional locals, CSS class patterns, and collection rendering with caching |
Views & Templates
ERB conventions for vanilla Rails applications.
Partial Organization
Lowest common ancestor — place partials at the highest shared directory:
app/views/cards/_card.html.erb # Shared by cards/show and cards/index
app/views/application/_flash.html.erb # Shared across controllers
app/views/cards/display/_compact.html.erb # Display variants
Never create deeply nested partials only used in one place.
Optional Locals
Use local_assigns.fetch with explicit defaults:
<% pinned = local_assigns.fetch(:pinned, false) %>
<% card = local_assigns.fetch(:card) %> <%# raises if missing %>
Not local_assigns[:x] || default (silent nil, ambiguous intent).
CSS Class Helper
Build classes with array + compact + join:
<div class="<%= [
'card',
('card--pinned' if card.pinned?),
('card--closed' if card.closed?)
].compact.join(' ') %>">
For complex cases: <div class="<%= token_list('card', 'card--pinned': card.pinned?) %>">
Collection Rendering
Always cache, always specify as::
<%= render partial: 'cards/card', collection: @cards, as: :card, cached: true %>
Turbo Streams in Views
Prepend/append with update for empty states:
<%= turbo_stream.before :cards, @card %>
<%= turbo_stream.update :cards_count, @cards.count %>
<%= turbo_stream.remove @card %>
See vanilla-rails-hotwire for dom_id, morph, and Stimulus patterns.
Stimulus in Views
Layer controllers on existing elements, don't add wrapper divs:
<body data-controller="keyboard shortcuts dropdown">
Quick Reference
| Pattern | Use |
|---|
local_assigns.fetch(:x, default) | Optional locals |
[...].compact.join(' ') | Conditional CSS classes |
cached: true, as: :item | Collection rendering |
turbo_stream.before + .update | Add + refresh related |
Red Flags
| Wrong | Right |
|---|
local_assigns[:x] || default | local_assigns.fetch(:x, default) |
| Wrapper div for Stimulus | Add controller to existing element |
render @cards without cache | render collection:, cached: true |
| Partial in deep nested path | Lowest common ancestor |
