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
|
module ActionController #:nodoc:
# Responder is responsible for exposing a resource to different mime requests,
# usually depending on the HTTP verb. The responder is triggered when
# <code>respond_with</code> is called. The simplest case to study is a GET request:
#
# class PeopleController < ApplicationController
# respond_to :html, :xml, :json
#
# def index
# @people = Person.find(:all)
# respond_with(@people)
# end
# end
#
# When a request comes in, for example for an XML response, three steps happen:
#
# 1) the responder searches for a template at people/index.xml;
#
# 2) if the template is not available, it will invoke <code>#to_xml</code> on the given resource;
#
# 3) if the responder does not <code>respond_to :to_xml</code>, call <code>#to_format</code> on it.
#
# === Builtin HTTP verb semantics
#
# The default Rails responder holds semantics for each HTTP verb. Depending on the
# content type, verb and the resource status, it will behave differently.
#
# Using Rails default responder, a POST request for creating an object could
# be written as:
#
# def create
# @user = User.new(params[:user])
# flash[:notice] = 'User was successfully created.' if @user.save
# respond_with(@user)
# end
#
# Which is exactly the same as:
#
# def create
# @user = User.new(params[:user])
#
# respond_to do |format|
# if @user.save
# flash[:notice] = 'User was successfully created.'
# format.html { redirect_to(@user) }
# format.xml { render :xml => @user, :status => :created, :location => @user }
# else
# format.html { render :action => "new" }
# format.xml { render :xml => @user.errors, :status => :unprocessable_entity }
# end
# end
# end
#
# The same happens for PUT and DELETE requests.
#
# === Nested resources
#
# You can supply nested resources as you do in <code>form_for</code> and <code>polymorphic_url</code>.
# Consider the project has many tasks example. The create action for
# TasksController would be like:
#
# def create
# @project = Project.find(params[:project_id])
# @task = @project.comments.build(params[:task])
# flash[:notice] = 'Task was successfully created.' if @task.save
# respond_with(@project, @task)
# end
#
# Giving an array of resources, you ensure that the responder will redirect to
# <code>project_task_url</code> instead of <code>task_url</code>.
#
# Namespaced and singleton resources require a symbol to be given, as in
# polymorphic urls. If a project has one manager which has many tasks, it
# should be invoked as:
#
# respond_with(@project, :manager, @task)
#
# Check <code>polymorphic_url</code> documentation for more examples.
#
class Responder
attr_reader :controller, :request, :format, :resource, :resources, :options
ACTIONS_FOR_VERBS = {
:post => :new,
:put => :edit
}
def initialize(controller, resources, options={})
@controller = controller
@request = controller.request
@format = controller.formats.first
@resource = resources.is_a?(Array) ? resources.last : resources
@resources = resources
@options = options
@action = options.delete(:action)
@default_response = options.delete(:default_response)
end
delegate :head, :render, :redirect_to, :to => :controller
delegate :get?, :post?, :put?, :delete?, :to => :request
# Undefine :to_json and :to_yaml since it's defined on Object
undef_method(:to_json) if method_defined?(:to_json)
undef_method(:to_yaml) if method_defined?(:to_yaml)
# Initializes a new responder an invoke the proper format. If the format is
# not defined, call to_format.
#
def self.call(*args)
new(*args).respond
end
# Main entry point for responder responsible to dispatch to the proper format.
#
def respond
method = :"to_#{format}"
respond_to?(method) ? send(method) : to_format
end
# HTML format does not render the resource, it always attempt to render a
# template.
#
def to_html
default_render
rescue ActionView::MissingTemplate => e
navigation_behavior(e)
end
# All other formats follow the procedure below. First we try to render a
# template, if the template is not available, we verify if the resource
# responds to :to_format and display it.
#
def to_format
default_render
rescue ActionView::MissingTemplate => e
raise unless resourceful?
api_behavior(e)
end
protected
# This is the common behavior for "navigation" requests, like :html, :iphone and so forth.
def navigation_behavior(error)
if get?
raise error
elsif has_errors? && default_action
render :action => default_action
else
redirect_to resource_location
end
end
# This is the common behavior for "API" requests, like :xml and :json.
def api_behavior(error)
if get?
display resource
elsif has_errors?
display resource.errors, :status => :unprocessable_entity
elsif post?
display resource, :status => :created, :location => resource_location
else
head :ok
end
end
# Checks whether the resource responds to the current format or not.
#
def resourceful?
resource.respond_to?(:"to_#{format}")
end
# Returns the resource location by retrieving it from the options or
# returning the resources array.
#
def resource_location
options[:location] || resources
end
# If a given response block was given, use it, otherwise call render on
# controller.
#
def default_render
@default_response.call
end
# Display is just a shortcut to render a resource with the current format.
#
# display @user, :status => :ok
#
# For XML requests it's equivalent to:
#
# render :xml => @user, :status => :ok
#
# Options sent by the user are also used:
#
# respond_with(@user, :status => :created)
# display(@user, :status => :ok)
#
# Results in:
#
# render :xml => @user, :status => :created
#
def display(resource, given_options={})
controller.render given_options.merge!(options).merge!(format => resource)
end
# Check whether the resource has errors.
#
def has_errors?
resource.respond_to?(:errors) && !resource.errors.empty?
end
# By default, render the <code>:edit</code> action for HTML requests with failure, unless
# the verb is POST.
#
def default_action
@action ||= ACTIONS_FOR_VERBS[request.method]
end
end
end
|
