lib/nestive/layout_helper.rb
module Nestive
# The Nestive LayoutHelper provides a handful of helper methods for use in your layouts and views.
#
# See the documentation for each individual method for detailed information, but at a high level,
# your parent layouts define `area`s of content. You can define an area and optionally add content
# to it at the same time using either a String, or a block:
#
# # app/views/layouts/global.html.erb
# <html>
# <head>
# <title><%= area :title, "MySite.com" %></title>
# </head>
# <body>
# <div id="content">
# <%= area :content %>
# </div>
# <div id="sidebar">
# <%= area :sidebar do %>
# <h2>About MySite.com</h2>
# <p>...</p>
# <% end %>
# </div>
# </body>
# </html>
#
# Your child layouts (or views) inherit and modify the parent by wrapping in an `extends` block
# helper. You can then either `append`, `prepend` or `replace` the content that has previously
# been assigned to each area by parent layouts.
#
# The `append`, `prepend` or `replace` helpers are *similar* to Rails' own `content_for`, which
# accepts content for the named area with either a String or with a block). They're different to
# `content_for` because they're only used modify the content assigned to the area, not retrieve it:
#
# # app/views/layouts/admin.html.erb
# <%= extends :global do %>
# <% prepend :title, "Admin :: " %>
# <% replace :sidebar do %>
# <h2>Quick Links</h2>
# <ul>
# <li>...</li>
# </ul>
# <% end %>
# <% end %>
#
# # app/views/admin/posts/index.html.erb
# <%= extends :admin do %>
# <% prepend :title, "Posts ::" %>
# <% replace :content do %>
# Normal view stuff goes here.
# <% end %>
# <% end %>
module LayoutHelper
# Declares that the current layour (or view) is inheriting from and extending another layout.
#
# @param [String] layout
# The base name of the file in `layouts/` that you wish to extend (eg `application` for `layouts/application.html.erb`)
#
# @example Extending the `application` layout to create an `admin` layout
#
# # app/views/layouts/admin.html.erb
# <%= extends :application do %>
# ...
# <% end %>
#
# @example Extending the `admin` layout in a view (you'll need to render the view with `layout: nil`)
#
# # app/controllers/admin/posts_controller.rb
# class Admin::PostsController < ApplicationController
# # You can disable Rails' layout rendering for all actions
# layout nil
#
# # Or disable Rails' layout rendering per-controller
# def index
# render layout: nil
# end
# end
#
# # app/views/admin/posts/index.html.erb
# <%= extends :admin do %>
# ...
# <% end %>
def extends(layout, &block)
# Make sure it's a string
layout = layout.to_s
# If there's no directory component, presume a plain layout name
layout = "layouts/#{layout}" unless layout.include?('/')
# Capture the content to be placed inside the extended layout
@view_flow.get(:layout).replace capture(&block).to_s
render file: layout
end
# Defines an area of content in your layout that can be modified or replaced by child layouts
# that extend it. You can optionally add content to an area using either a String, or a block.
#
# Areas are declared in a parent layout and modified by a child layout, but since Nestive
# allows for multiple levels of inheritance, a child layout can also declare an area for it's
# children to modify.
#
# @example Define an area without adding content to it:
# <%= area :sidebar %>
#
# @example Define an area and add a String of content to it:
# <%= area :sidebar, "Some content." %>
#
# @example Define an area and add content to it with a block:
# <%= area :sidebar do %>
# Some content.
# <% end %>
#
# @example Define an area in a child layout:
# <%= extends :global do %>
# <%= area :sidebar do %>
# Some content.
# <% end %>
# <% end %>
#
# @param [Symbol] name
# A unique name to identify this area of content.
#
# @param [String] content
# An optional String of content to add to the area as you declare it.
def area(name, content=nil, &block)
content = capture(&block) if block_given?
append name, content
render_area name
end
# Appends content to an area previously defined or modified in parent layout(s). You can provide
# the content using either a String, or a block.
#
# @example Appending content with a String
# <% append :sidebar, "Some content." %>
#
# @example Appending content with a block:
# <% append :sidebar do %>
# Some content.
# <% end %>
#
# @param [Symbol] name
# A name to identify the area of content you wish to append to
#
# @param [String] content
# Optionally provide a String of content, instead of a block. A block will take precedence.
def append(name, content=nil, &block)
content = capture(&block) if block_given?
add_instruction_to_area name, :push, content
end
# Prepends content to an area previously declared or modified in parent layout(s). You can
# provide the content using either a String, or a block.
#
# @example Prepending content with a String
# <% prepend :sidebar, "Some content." %>
#
# @example Prepending content with a block:
# <% prepend :sidebar do %>
# Some content.
# <% end %>
#
# @param [Symbol] name
# A name to identify the area of content you wish to prepend to
#
# @param [String] content
# Optionally provide a String of content, instead of a block. A block will take precedence.
def prepend(name, content=nil, &block)
content = capture(&block) if block_given?
add_instruction_to_area name, :unshift, content
end
# Replaces the content of an area previously declared or modified in parent layout(s). You can
# provide the content using either a String, or a block.
#
# @example Replacing content with a String
# <% replace :sidebar, "New content." %>
#
# @example Replacing content with a block:
# <% replace :sidebar do %>
# New content.
# <% end %>
#
# @param [Symbol] name
# A name to identify the area of content you wish to replace
#
# @param [String] content
# Optionally provide a String of content, instead of a block. A block will take precedence.
def replace(name, content=nil, &block)
content = capture(&block) if block_given?
add_instruction_to_area name, :replace, [content]
end
# Purge the content of an area previously declared or modified in parent layout(s).
#
# @example Purge content
# <% purge :sidebar %>
#
# @param names
# A list of area names to purge
def purge(*names)
names.each{ |name| replace(name, nil)}
end
private
# We record the instructions (declaring, appending, prepending and replacing) for an area of
# content into an array that we can later retrieve and replay. Instructions are stored in an
# instance variable Hash `@_area_for`, with each key representing an area name, and each value
# an Array of instructions. Each instruction is a two element array containing a instruction
# method (eg `:push`, `:unshift`, `:replace`) and a value (content String).
#
# @_area_for[:sidebar] # => [ [:push,"World"], [:unshift,"Hello"] ]
#
# Due to the way we extend layouts (render the parent layout after the child), the instructions
# are captured in reverse order. `render_area` reversed them and plays them back at rendering
# time.
#
# @example
# add_instruction_to_area(:sidebar, :push, "More content.")
def add_instruction_to_area(name, instruction, value)
@_area_for ||= {}
@_area_for[name] ||= []
@_area_for[name] << [instruction, value]
nil
end
# Take the instructions we've gathered for the area and replay them one after the other on
# an empty array. These instructions will push, unshift or replace items into our output array,
# which we then join and mark as html_safe.
#
# These instructions are reversed and replayed when we render the block (rather than as they
# happen) due to the way they are gathered by the layout extension process (in reverse).
def render_area(name)
[].tap do |output|
@_area_for.fetch(name, []).reverse_each do |method_name, content|
output.public_send method_name, content
end
end.join.html_safe
end
end
end