Rails 使用 Paperclip 上传图片

转移 http://aikin.me/2014/02/20/rails-paperclip/ 

 

Paperclip是 Rails 的一个上传图片插件，它和ImageMagick联合使用，可以很方便的实现图片上传并切割指定大小的功能，使整个图片上传过程非常简单，还会将上传的图片保存在public文件夹下。

   1.下载paperclip gem包

 （1）在Gemfile中写上

gem 'paperclip'

 

  （2）在终端运行

bundle install

   

    2.使用paperclip

  （1）在终端输入：

rails g paperclip image_news image

   这样就会在原先的 image_news model中增加image属性，同时在app/db/migrate 文件夹下会

   新建xxxxxxx_add_attachment_image_to_image_news.rb 文件内容：

class AddAttachmentImageToImageNews < ActiveRecord::Migration
  def self.up
    change_table :image_news do |t|
      t.attachment :image
    end
  end

  def self.down
    drop_attached_file :image_news, :image
  end

end

 

  （2）再对数据库迁移，终端输入：

rake db:migrate

   

   如果你原先的image_news model 中没有其他属性，那么在schema.rb文件中：

ActiveRecord::Schema.define(version:xxxxxxx) do

  create_table "image_news", force: true do |t|
    t.datetime "created_at"
    t.datetime "updated_at"
    t.string   "image_file_name"
    t.string   "image_content_type"
    t.integer  "image_file_size"
    t.datetime "image_updated_at"
  end

end

 

 （3）接着在image_news.rb文件中写上：

class ImageNews < ActiveRecord::Base
  has_attached_file :image,                                                                          //:styles => { :small => "150x150>"},                
                    :url  => '/images/:id/:style/:basename.:extension',
                    :path => ':rails_root/public/images/:id/:style/:basename.:extension'
  validates_attachment_presence :image
  validates_attachment_size :image, :less_than => 5.megabytes
  validates_attachment_content_type :image, :content_type => %w(image/jpeg image/png)
end

   上面代码，要使用 :styles 就必须要确认是否有装 imageMagick,如果没装就会报错。

   还有 :path :rails_root/public 后面的必须和 :url相同，就像这里的

   'images/:style/:basename.:extension' 

    

:rails_root 
    The path to the Rails application.（当前Rails程序的路径，等同于RAILS_PATH的值。） 
:rails_env 
    The current environment (e.g. development, production)（当前运行环境，如：development，production） 
:class 
    The class name of the model that the attachment is part of, underscored and pluralised for your convenience.（文件拥有者的类名的复数形式，多个单词间以下划线连接。） 
:basename 
    The name of the originally uploaded file without its extension.（上传的文件原始的名字，不带扩展名。） 
:extension 
    The file extension of the originally uploaded file.（上传的文件的扩展名） 
:id 
    The ID of the model that the attachment is part of.（文件拥有者的id） 
:id_partition 
    The same as :id but formatted as a string using ID partitioning.（和:id一样，但结果是用ID partitioning格式化过的。） 
:attachment 
    The name of the attachment attribute (defined in the call to has_attached_file) downcased and pluralised for your enjoyment.（文件作为拥有者的属性的属性名，也就是跟在has_attached_file后面的那个名字，小写、复数形式。） 
:style 
    The current style of the attachment file being processed (e.g. in the ‘discarding an uploaded image‘ example above the :style would be one of ‘original’ or ‘small’) （文件被以某种样式处理的样式名，该选项用于图片处理。）

    

 

   (4) 在controller（controllers/image_upload_controller.rb）里写上：

class ImageUploadController < ApplicationController

  def image_upload_view
    @image_news = ImageNews.new
  end

  def upload
    @image_news = ImageNews.new
    @image_news.image = params[:image_news][:image]
    @image_news.save
    redirect_to(:action => 'image_show_view', :id => @image_news.id)
  end

  def image_show_view
    @image_news = ImageNews.find(params[:id])
  end

end

   

   (5) 在view(views/image_upload_view.html.erb)写上：

<div style="background: #F5F5F5; width: 659px; padding: 50px; margin: 100px auto auto auto">
  <%= form_for @image_news, :url =>{:action => 'upload'}, :html => {:multipart => true} do |f|  %>
      <p>请选择图片：</p>
      <%= f.file_field :image%>
      <%= f.submit '上传' %>
  <% end %>
</div>

 （6）在view/image_show_view.html.erb写上：

<div style="margin: 100px 80px 100px 500px">
 <%= image_tag @image_news.image.url%>
</div>

    

    (7) 安装ImageMagick (Mac OS X 10.8.5) 安装很成功、方便，不过得最先装xcode。

curl -O ftp://ftp.imagemagick.org/pub/ImageMagick/ImageMagick.tar.gz
tar -zxf ImageMagick.tar.gz
cd ImageMagick-*/
./configure --prefix=/opt/local
make
sudo make install

    也可以用Homebrew安装。   

 

    参考：http://yuan.iteye.com/blog/604174

              http://huacnlee.com/blog/rails-plugin-paperclip-for-image-upload/

              http://railscasts.com/episodes/134-paperclip

              http://elf8848.iteye.com/blog/455675