Class: Curly::Presenter

Inherits:
Object
  • Object
show all
Defined in:
lib/curly/presenter.rb

Overview

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"

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(context, options = {}) ⇒ Presenter

Initializes the presenter with the given context and options.

context - An ActionView::Base context. options - A Hash of options given to the presenter.



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# 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

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method, *args, &block) ⇒ Object (private)

Delegates private method calls to the current view context.

The view context, an instance of ActionView::Base, is set by Rails.



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# File 'lib/curly/presenter.rb', line 344

def method_missing(method, *args, &block)
  @_context.public_send(method, *args, &block)
end

Class Method Details

.available_components ⇒ Object

A list of components available to templates rendered with the presenter.

Returns an Array of String component names.



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# 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

.cache_key ⇒ Object

The cache key for the presenter class. Includes all dependencies as well.

Returns a String cache key.



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# File 'lib/curly/presenter.rb', line 282

def cache_key
  @cache_key ||= compute_cache_key
end

.component_available?(name) ⇒ Boolean

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.

Returns:

  • (Boolean) 


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# File 'lib/curly/presenter.rb', line 222

def component_available?(name)
  available_components.include?(name)
end

.dependencies ⇒ Object

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.



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# 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

.depends_on(*dependencies) ⇒ Object

Indicate that the presenter depends a list of other views.

deps - A list of String view paths that the presenter depends on.

Returns nothing.



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# File 'lib/curly/presenter.rb', line 262

def depends_on(*dependencies)
  @dependencies ||= SortedSet.new
  @dependencies.merge(dependencies)
end

.presenter_for_name(name, namespace_prefixes = to_s.split('::')) ⇒ Object

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).



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# 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

.presenter_for_path(path) ⇒ Object

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.



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# 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

.presenter_name_for_path(path) ⇒ Object

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.



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# File 'lib/curly/presenter.rb', line 149

def presenter_name_for_path(path)
  "#{path}_presenter".camelize
end

.version(version = nil) ⇒ Object

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.



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# File 'lib/curly/presenter.rb', line 273

def version(version = nil)
  @version = version if version.present?
  @version || 0
end

Instance Method Details

#cache_duration ⇒ Object

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.



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# File 'lib/curly/presenter.rb', line 133

def cache_duration
  nil
end

#cache_key ⇒ Object

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.



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# File 'lib/curly/presenter.rb', line 100

def cache_key
  nil
end

#cache_options ⇒ Object

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.



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# File 'lib/curly/presenter.rb', line 115

def cache_options
  {}
end

#setup! ⇒ Object

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.



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# File 'lib/curly/presenter.rb', line 82

def setup!
  # Does nothing.
end