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| -rw-r--r-- | guides/source/layouts_and_rendering.md | 39 |
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diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md index a2ae4ea59e..43cc958cb1 100644 --- a/guides/source/layouts_and_rendering.md +++ b/guides/source/layouts_and_rendering.md @@ -296,6 +296,7 @@ Calls to the `render` method generally accept five options: * `:location` * `:status` * `:formats` +* `:variants` ##### The `:content_type` Option @@ -417,6 +418,44 @@ render formats: [:json, :xml] If a template with the specified format does not exist an `ActionView::MissingTemplate` error is raised. +##### The `:variants` Option + +This tells rails to look for template variations of the same format. +You can specify a list of variants by passing the `:variants` option with a symbol or an array. + +An example of use would be this. + +```ruby +# called in HomeController#index +render variants: [:mobile, :desktop] +``` + +With this set of variants Rails will look for the following set of templates and use the first that exists. + +- `app/views/home/index.html+mobile.erb` +- `app/views/home/index.html+desktop.erb` +- `app/views/home/index.html.erb` + +If a template with the specified format does not exist an `ActionView::MissingTemplate` error is raised. + +Instead of setting the variant on the render call you may also set it on the request object in your controller action. + +```ruby +def index + request.variant = determine_variant +end + +private + +def determine_variant + variant = nil + # some code to determine the variant(s) to use + variant = :mobile if session[:use_mobile] + + variant +end +``` + #### Finding Layouts To find the current layout, Rails first looks for a file in `app/views/layouts` with the same base name as the controller. For example, rendering actions from the `PhotosController` class will use `app/views/layouts/photos.html.erb` (or `app/views/layouts/photos.builder`). If there is no such controller-specific layout, Rails will use `app/views/layouts/application.html.erb` or `app/views/layouts/application.builder`. If there is no `.erb` layout, Rails will use a `.builder` layout if one exists. Rails also provides several ways to more precisely assign specific layouts to individual controllers and actions. |