Exposures
Define exposures within your view to declare and prepare the values to be passed to the template, decorated as parts.
An exposure can take a block:
class MyView < Dry::View
expose :users do
user_repo.listing
end
end
Or refer to an instance method:
class MyView < Dry::View
expose :users
private
def users
user_repo.listing
end
end
Or allow a matching value from the input data to pass through to the view:
class MyView < Dry::View
# With no matching instance method, passes the `users:` argument provided to
# `#call` straight to the template
expose :users
end
Accessing input data
If your exposure needs to work with input data (i.e. the arguments passed to the view’s #call), specify these as keyword arguments for your exposure block. Make this a required keyword argument if you require the data passed to the view’s #call:
class MyView < Dry::View
expose :users do |page:|
user_repo.listing(page: page)
end
end
The same applies to instance methods acting as exposures:
class MyView < Dry::View
expose :users
private
def users(page:)
user_repo.listing(page: page)
end
end
Specifying defaults
To make input data optional, provide a default value for the keyword argument (either nil or something more meaningful):
class MyView < Dry::View
expose :users do |page: 1|
user_repo.listing(page: page)
end
end
If your exposure passes through input data directly, use the default: option:
class MyView < Dry::View
# With no matching instance method, passes the `users:` argument to `#call`
# straight to the template
expose :users, default: []
end
Accessing the context
To access the context object from an exposure, include a context: keyword parameter:
expose :articles do |context:|
article_repo.listing_for_user(context.current_user)
end
Depending on other exposures
Sometimes you may want to prepare data for other exposures to use. You can depend on another exposure by naming it as a positional argument for your exposure block or method.
class MyView < Dry::View::Controller
expose :users do |page:|
user_repo.listing(page: page)
end
expose :user_count do |users|
users.to_a.length
end
end
In this example, the user_count exposure has access to the value of the users value since it named the exposure as a positional argument. The users value is at this point will already be decorated by its part object.
Exposure dependencies (positional arguments) and input data (keyword arguments) can also be provided together:
expose :user_count do |users, count_title: "Admins count"|
"#{count_title}: #{users.to_a.length}"
end
Layout exposures
Exposure values are made available only to the template by default. To make an exposure available to the layout, specify the layout: true option:
expose :users, layout: true do |page:|
user_repo.listing(page: page)
end
Private exposures
You can create private exposures that are not passed to the template. This is helpful if you have an exposure that others will depend on, but is not otherwise needed in the template. Use private_expose for this:
class MyView < Dry::View::Controller
private_expose :user_listing do
user_repo.listing
end
expose :users do |user_listing|
# does something with user_listing
end
expose :user_count do |user_listing|
# also needs to work with user_listing
end
end
In this example, only users and user_count will be passed to the template.
Undecorated exposures
You can create an exposure whose value is not decorated by a part. This may be helpful when your exposure returns a simpler "primitive" object that requires no extra behaviour, like a number or a string. To do this, pass the decorate: false option.
expose :page_number, decorate: false