1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
|
require 'active_support/core_ext/string/output_safety'
module ActionView
# = Action View Capture Helper
module Helpers
# CaptureHelper exposes methods to let you extract generated markup which
# can be used in other parts of a template or layout file.
#
# It provides a method to capture blocks into variables through capture and
# a way to capture a block of markup for use in a layout through content_for.
module CaptureHelper
# The capture method allows you to extract part of a template into a
# variable. You can then use this variable anywhere in your templates or layout.
#
# The capture method can be used in ERB templates...
#
# <% @greeting = capture do %>
# Welcome to my shiny new web page! The date and time is
# <%= Time.now %>
# <% end %>
#
# ...and Builder (RXML) templates.
#
# @timestamp = capture do
# "The current timestamp is #{Time.now}."
# end
#
# You can then use that variable anywhere else. For example:
#
# <html>
# <head><title><%= @greeting %></title></head>
# <body>
# <b><%= @greeting %></b>
# </body></html>
#
def capture(*args)
value = nil
buffer = with_output_buffer { value = yield(*args) }
if string = buffer.presence || value and string.is_a?(String)
ERB::Util.html_escape string
end
end
# Calling content_for stores a block of markup in an identifier for later use.
# In order to access this stored content in other templates, helper modules
# or the layout, you would pass the identifier as an argument to <tt>content_for</tt>.
#
# Note: <tt>yield</tt> can still be used to retrieve the stored content, but calling
# <tt>yield</tt> doesn't work in helper modules, while <tt>content_for</tt> does.
#
# <% content_for :not_authorized do %>
# alert('You are not authorized to do that!')
# <% end %>
#
# You can then use <tt>content_for :not_authorized</tt> anywhere in your templates.
#
# <%= content_for :not_authorized if current_user.nil? %>
#
# This is equivalent to:
#
# <%= yield :not_authorized if current_user.nil? %>
#
# <tt>content_for</tt>, however, can also be used in helper modules.
#
# module StorageHelper
# def stored_content
# content_for(:storage) || "Your storage is empty"
# end
# end
#
# This helper works just like normal helpers.
#
# <%= stored_content %>
#
# You can also use the <tt>yield</tt> syntax alongside an existing call to
# <tt>yield</tt> in a layout. For example:
#
# <%# This is the layout %>
# <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
# <head>
# <title>My Website</title>
# <%= yield :script %>
# </head>
# <body>
# <%= yield %>
# </body>
# </html>
#
# And now, we'll create a view that has a <tt>content_for</tt> call that
# creates the <tt>script</tt> identifier.
#
# <%# This is our view %>
# Please login!
#
# <% content_for :script do %>
# <script>alert('You are not authorized to view this page!')</script>
# <% end %>
#
# Then, in another view, you could to do something like this:
#
# <%= link_to 'Logout', action: 'logout', remote: true %>
#
# <% content_for :script do %>
# <%= javascript_include_tag :defaults %>
# <% end %>
#
# That will place +script+ tags for your default set of JavaScript files on the page;
# this technique is useful if you'll only be using these scripts in a few views, like,
# for example, external libs such as Google Maps.
#
# Note that content_for concatenates (default) the blocks it is given for a particular
# identifier in order. For example:
#
# <% content_for :navigation do %>
# <li><%= link_to 'Home', action: 'index' %></li>
# <% end %>
#
# And in other place:
#
# <% content_for :navigation do %>
# <li><%= link_to 'Login', action: 'login' %></li>
# <% end %>
#
# Then, in another template or layout, this code would render both links in order:
#
# <ul><%= content_for :navigation %></ul>
#
# If the flush parameter is true content_for replaces the blocks it is given. For example:
#
# <% content_for :navigation do %>
# <li><%= link_to 'Home', action: 'index' %></li>
# <% end %>
#
# <%# Add some other content, or use a different template: %>
#
# <% content_for :navigation, flush: true do %>
# <li><%= link_to 'Login', action: 'login' %></li>
# <% end %>
#
# Then, in another template or layout, this code would render only the last link:
#
# <ul><%= content_for :navigation %></ul>
#
# Lastly, simple content can be passed as a parameter:
#
# <% content_for :script, javascript_include_tag(:defaults) %>
#
# WARNING: content_for is ignored in caches since there won't be processed.
# So you shouldn't use it for elements that will be fragment cached.
def content_for(name, content = nil, options = {}, &block)
if content || block_given?
if block_given?
options = content if content
content = capture(&block)
end
if content
options[:flush] ? @view_flow.set(name, content) : @view_flow.append(name, content)
end
nil
else
@view_flow.get(name)
end
end
# The same as +content_for+ but when used with streaming flushes
# straight back to the layout. In other words, if you want to
# concatenate several times to the same buffer when rendering a given
# template, you should use +content_for+, if not, use +provide+ to tell
# the layout to stop looking for more contents.
def provide(name, content = nil, &block)
content = capture(&block) if block_given?
result = @view_flow.append!(name, content) if content
result unless content
end
# content_for? simply checks whether any content has already been captured
# yet using content_for. Useful to render parts of your layout differently
# based on what is in your views.
#
# Perhaps you will use different css in you layout if no content_for :right_column
#
# <%# This is the layout %>
# <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
# <head>
# <title>My Website</title>
# <%= yield :script %>
# </head>
# <body class="<%= content_for?(:right_col) ? 'one-column' : 'two-column' %>">
# <%= yield %>
# <%= yield :right_col %>
# </body>
# </html>
def content_for?(name)
@view_flow.get(name).present?
end
# Use an alternate output buffer for the duration of the block.
# Defaults to a new empty string.
def with_output_buffer(buf = nil) #:nodoc:
unless buf
buf = ActionView::OutputBuffer.new
buf.force_encoding(output_buffer.encoding) if output_buffer
end
self.output_buffer, old_buffer = buf, output_buffer
yield
output_buffer
ensure
self.output_buffer = old_buffer
end
# Add the output buffer to the response body and start a new one.
def flush_output_buffer #:nodoc:
if output_buffer && !output_buffer.empty?
response.stream.write output_buffer
self.output_buffer = output_buffer.respond_to?(:clone_empty) ? output_buffer.clone_empty : output_buffer[0, 0]
nil
end
end
end
end
end
|
