add formData support

test-app/app/controllers/blogs_controller.rb

@@ -4,10 +4,19 @@ class BlogsController < ApplicationController
 
   # POST /blogs
   def create
-    @blog = Blog.create(params.require(:blog).permit(:title, :content))
+    thumbnail = save_uploaded_file(params[:blog][:thumbnail])
+    @blog = Blog.create(params.require(:blog).permit(:title, :content).merge(:thumbnail => thumbnail))
     respond_with @blog
   end
 
+  # Put /blogs/1
+  def upload
+    @blog = Blog.find_by_id(params[:id])
+    return head :not_found if @blog.nil?
+    @blog.thumbnail = save_uploaded_file params[:file]
+    head @blog.save ? :ok : :unprocsessible_entity
+  end
+
   # GET /blogs
   def index
     @blogs = Blog.all
@@ -24,4 +33,14 @@ class BlogsController < ApplicationController
     respond_with @blog, status: :not_found and return unless @blog
     respond_with @blog
   end
+
+  private
+
+  def save_uploaded_file(field)
+    return if field.nil?
+    require 'fileutils'
+    file = File.join('tmp', field.original_filename)
+    FileUtils.cp field.tempfile.path, file
+    field.original_filename
+  end
 end