module NestiveRails::LayoutHelper

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 %>

Public Instance Methods

append(name, content = nil, &block) click to toggle source

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.
# File lib/nestive-rails/layout_helper.rb, line 158
def append(name, content = nil, &block)
  content = capture(&block) if block_given?
  add_instruction_to_area name, :push, content
end
area(name, content = nil, &block) click to toggle source

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.
# File lib/nestive-rails/layout_helper.rb, line 135
def area(name, content = nil, &block)
  content = capture(&block) if block_given?
  append name, content
  render_area name
end
extends(layout, &block) click to toggle source

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 %>
# File lib/nestive-rails/layout_helper.rb, line 91
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
prepend(name, content = nil, &block) click to toggle source

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.
# File lib/nestive-rails/layout_helper.rb, line 180
def prepend(name, content = nil, &block)
  content = capture(&block) if block_given?
  add_instruction_to_area name, :unshift, content
end
purge(*names) click to toggle source

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
# File lib/nestive-rails/layout_helper.rb, line 215
def purge(*names)
  names.each { |name| replace(name, nil) }
end
replace(name, content = nil, &block) click to toggle source

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.
# File lib/nestive-rails/layout_helper.rb, line 202
def replace(name, content = nil, &block)
  content = capture(&block) if block_given?
  add_instruction_to_area name, :replace, [content]
end

Private Instance Methods

add_instruction_to_area(name, instruction, value) click to toggle source

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.")
# File lib/nestive-rails/layout_helper.rb, line 237
def add_instruction_to_area(name, instruction, value)
  @_area_for ||= {}
  @_area_for[name] ||= []
  @_area_for[name] << [instruction, value]
  nil
end
render_area(name) click to toggle source

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).

# File lib/nestive-rails/layout_helper.rb, line 252
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