From 8c10764be79ee1f9b020766fdea7c69d74f2ab81 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ga=C3=ABl=20Deest?= <gael.deest@gmail.com>
Date: Thu, 18 Mar 2010 15:01:24 +0100
Subject: [PATCH] Adding a 'build' method to the ActiveResource class, to build a new resource from the default values of the remote site. This fixes two issues:

- When using the RESTful form_for helper with new ActiveResource instance, creating fields for uninitialized attributes would result in a NoMethodError exception.
- Remote default values can now be used to populate forms.

Usage: Simply call Resource.build instead of Resource.new when using ActiveResource.

[#4155 state:committed]
---
 activeresource/lib/active_resource/base.rb |   34 ++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/activeresource/lib/active_resource/base.rb b/activeresource/lib/active_resource/base.rb
index b841108..16dda18 100644
--- a/activeresource/lib/active_resource/base.rb
+++ b/activeresource/lib/active_resource/base.rb
@@ -625,6 +625,22 @@ module ActiveResource
         "#{prefix(prefix_options)}#{collection_name}/#{id}.#{format.extension}#{query_string(query_options)}"
       end
 
+      # Gets the new element path for REST resources.
+      #
+      # ==== Options
+      # * +prefix_options+ - A hash to add a prefix to the request for nested URLs (e.g., <tt>:account_id => 19</tt>
+      #   would yield a URL like <tt>/accounts/19/purchases/new.xml</tt>).
+      #
+      # ==== Examples
+      #   Post.new_element_path
+      #   # => /posts/new.xml
+      #
+      #   Comment.collection_path(:post_id => 5)
+      #   # => /posts/5/comments/new.xml
+      def new_element_path(prefix_options = {})
+        "#{prefix(prefix_options)}#{collection_name}/new.#{format.extension}"
+      end
+
       # Gets the collection path for the REST resources.  If the +query_options+ parameter is omitted, Rails
       # will split from the +prefix_options+.
       #
@@ -653,6 +669,19 @@ module ActiveResource
 
       alias_method :set_primary_key, :primary_key=  #:nodoc:
 
+      # Builds a new, unsaved record using the default values from the remote server so
+      # that it can be used with RESTful forms.
+      #
+      # ==== Options
+      # * +attributes+ - A hash that overrides the default values from the server.
+      #
+      # Returns the new resource instance.
+      #
+      def build(attributes = {})
+        attrs = connection.get("#{new_element_path}").merge(attributes)
+        self.new(attrs)
+      end
+
       # Creates a new resource instance and makes a request to the remote service
       # that it be saved, making it equivalent to the following simultaneous calls:
       #
@@ -933,6 +962,7 @@ module ActiveResource
     def initialize(attributes = {})
       @attributes     = {}.with_indifferent_access
       @prefix_options = {}
+      
       load(attributes)
     end
 
@@ -1346,6 +1376,10 @@ module ActiveResource
         self.class.element_path(to_param, options || prefix_options)
       end
 
+      def new_element_path
+        self.class.new_element_path(prefix_options)
+      end
+
       def collection_path(options = nil)
         self.class.collection_path(options || prefix_options)
       end
-- 
1.7.0