class Curly::Presenter
A base class that can be subclassed by concrete presenters.
A Curly
presenter is responsible for delivering data to templates, in the form of simple strings. Each public instance method on the presenter class can be referenced in a template. When a template is evaluated with a presenter, the referenced methods will be called with no arguments, and the returned strings inserted in place of the components in the template.
Note that strings that are not HTML safe will be escaped.
A presenter is always instantiated with a context to which it delegates unknown messages, usually an instance of ActionView::Base provided by Rails. See Curly::TemplateHandler
for a typical use.
Examples
class BlogPresenter < Curly::Presenter presents :post def title @post.title end def body markdown(@post.body) end def author @post.author.full_name end end presenter = BlogPresenter.new(context, post: post) presenter.author #=> "Jackie Chan"
Public Class Methods
A list of components available to templates rendered with the presenter.
Returns an Array of String component names.
# File lib/curly/presenter.rb, line 229 def available_components @_available_components ||= begin methods = public_instance_methods - Curly::Presenter.public_instance_methods methods.map(&:to_s) end end
The cache key for the presenter class. Includes all dependencies as well.
Returns a String cache key.
# File lib/curly/presenter.rb, line 282 def cache_key @cache_key ||= compute_cache_key end
Whether a component is available to templates rendered with the presenter.
Templates have components which correspond with methods defined on the presenter. By default, only public instance methods can be referenced, and any method defined on Curly::Presenter
itself cannot be referenced. This means that methods such as `#cache_key` and inspect are not available. This is done for safety purposes.
This policy can be changed by overriding this method in your presenters.
name - The String name of the component.
Returns true if the method can be referenced by a template,
false otherwise.
# File lib/curly/presenter.rb, line 222 def component_available?(name) available_components.include?(name) end
The set of view paths that the presenter depends on.
Examples
class Posts::ShowPresenter < Curly::Presenter version 2 depends_on 'posts/comment', 'posts/comment_form' end Posts::ShowPresenter.dependencies #=> ['posts/comment', 'posts/comment_form']
Returns a Set of String view paths.
# File lib/curly/presenter.rb, line 249 def dependencies # The base presenter doesn't have any dependencies. return SortedSet.new if self == Curly::Presenter @dependencies ||= SortedSet.new @dependencies.union(superclass.dependencies) end
Indicate that the presenter depends a list of other views.
deps - A list of String view paths that the presenter depends on.
Returns nothing.
# File lib/curly/presenter.rb, line 262 def depends_on(*dependencies) @dependencies ||= SortedSet.new @dependencies.merge(dependencies) end
Initializes the presenter with the given context and options.
context - An ActionView::Base context. options - A Hash of options given to the presenter.
# File lib/curly/presenter.rb, line 46 def initialize(context, options = {}) @_context = context options.stringify_keys! self.class.presented_names.each do |name| value = options.fetch(name) do default_values.fetch(name) do block = default_blocks.fetch(name) do raise ArgumentError.new("required identifier `#{name}` missing") end instance_exec(name, &block) end end instance_variable_set("@#{name}", value) end end
Retrieve the named presenter with consideration for object scope. The namespace_prefixes are to acknowledge that sometimes we will have a subclass of Curly::Presenter
receiving the .presenter_for_name and other times we will not (when we are receiving this message by way of the .presenter_for_path method).
# File lib/curly/presenter.rb, line 173 def presenter_for_name(name, namespace_prefixes = to_s.split('::')) full_class_name = name.camelcase << "Presenter" relative_namespace = full_class_name.split("::") class_name = relative_namespace.pop namespace = namespace_prefixes + relative_namespace # Because Rails' autoloading mechanism doesn't work properly with # namespace we need to loop through the namespace ourselves. Ideally, # `X::Y.const_get("Z")` would autoload `X::Z`, but only `X::Y::Z` is # attempted by Rails. This sucks, and hopefully we can find a better # solution in the future. begin full_name = namespace.join("::") << "::" << class_name full_name.constantize rescue NameError => e # Due to the way the exception hirearchy works, we need to check # that this exception is actually a `NameError` - since other # classes can inherit `NameError`, rescue will actually rescue # those classes as being under `NameError`, causing this block to # be executed for classes that aren't `NameError`s (but are rather # subclasses of it), which isn't the desired behavior. This # prevents anything but `NameError`s from triggering the resulting # code. `NoMethodError` is actually a subclass of `NameError`, # so a typo in a file (e.g. `present` instead of `presents`) can # cause the library to act as if the class was never defined. raise unless e.class == NameError if namespace.empty? raise Curly::PresenterNameError.new(e, name) end namespace.pop retry end end
Returns the presenter class for the given path.
path - The String path of a template.
Returns the Class or nil if the constant cannot be found.
# File lib/curly/presenter.rb, line 158 def presenter_for_path(path) begin # Assume that the path can be derived without a prefix; In other words # from the given path we can look up objects by namespace. presenter_for_name(path.camelize, []) rescue Curly::PresenterNameError nil end end
The name of the presenter class for a given view path.
path - The String path of a view.
Examples
Curly::TemplateHandler.presenter_name_for_path("foo/bar") #=> "Foo::BarPresenter"
Returns the String name of the matching presenter class.
# File lib/curly/presenter.rb, line 149 def presenter_name_for_path(path) "#{path}_presenter".camelize end
Get or set the version of the presenter.
version - The Integer version that should be set. If nil, no version
is set.
Returns the current Integer version of the presenter.
# File lib/curly/presenter.rb, line 273 def version(version = nil) @version = version if version.present? @version || 0 end
Private Class Methods
# File lib/curly/presenter.rb, line 288 def compute_cache_key dependency_cache_keys = dependencies.map do |path| if presenter = presenter_for_path(path) presenter.cache_key else path end end [name, version, dependency_cache_keys].flatten.join("/") end
# File lib/curly/presenter.rb, line 320 def exposes_helper(*methods) methods.each do |method_name| define_method(method_name) do |*args| @_context.public_send(method_name, *args) end end end
# File lib/curly/presenter.rb, line 300 def presents(*args, **options, &block) if options.key?(:default) && block_given? raise ArgumentError, "Cannot provide both `default:` and block" end self.presented_names += args.map(&:to_s) if options.key?(:default) args.each do |arg| self.default_values = default_values.merge(arg.to_s => options[:default]).freeze end end if block_given? args.each do |arg| self.default_blocks = default_blocks.merge(arg.to_s => block).freeze end end end
Public Instance Methods
The duration that the view should be cached for. Only relevant if `#cache_key` returns a non nil value.
If nil, the view will not have an expiration time set. See also `#cache_options` for a more flexible way to set cache options.
Examples
def cache_duration 10.minutes end
Returns the Fixnum duration of the cache item, in seconds, or nil if no
duration should be set.
# File lib/curly/presenter.rb, line 133 def cache_duration nil end
The key that should be used to cache the view.
Unless `#cache_key` returns nil, the result of rendering the template that the presenter supports will be cached. The return value will be part of the final cache key, along with a digest of the template itself.
Any object can be used as a cache key, so long as it
-
is a String,
-
responds to
cache_key
itself, or -
is an Array or a Hash whose items themselves fit either of these criteria.
Returns the cache key Object or nil if no caching should be performed.
# File lib/curly/presenter.rb, line 100 def cache_key nil end
The options that should be passed to the cache backend when caching the view. The exact options may vary depending on the backend you're using.
The most common option is `:expires_in`, which controls the duration of time that the cached view should be considered fresh. Because it's so common, you can set that option simply by defining `#cache_duration`.
Note: if you set the `:expires_in` option through this method, the `#cache_duration` value will be ignored.
Returns a Hash.
# File lib/curly/presenter.rb, line 115 def cache_options {} end
Sets up the view.
Override this method in your presenter in order to do setup before the template is rendered. One use case is to call `content_for` in order to inject content into other templates, e.g. a layout.
Examples
class Posts::ShowPresenter < Curly::Presenter presents :post def setup! content_for :page_title, @post.title end end
Returns nothing.
# File lib/curly/presenter.rb, line 82 def setup! # Does nothing. end
Private Instance Methods
Delegates private method calls to the current view context.
The view context, an instance of ActionView::Base, is set by Rails.
# File lib/curly/presenter.rb, line 344 def method_missing(method, *args, &block) @_context.public_send(method, *args, &block) end
Tells ruby (and developers) what methods we can accept.
# File lib/curly/presenter.rb, line 349 def respond_to_missing?(method, include_private = false) @_context.respond_to?(method, false) end