使用桥接模式c ++实现复制构造函数(Implement copy constructor with bridge pattern c++)

 
 
 这是从头开始在rails 4中使用carrierwave上载多个图像的解决方案 
 
 
 或者你可以找到工作演示： 多个附件Rails 4 
 
 
 要按照这些步骤做。 
 
rails new multiple_image_upload_carrierwave
 
 在宝石文件 
 
gem 'carrierwave'
bundle install
rails generate uploader Avatar 
 
 创建脚手架 
 
rails generate scaffold post title:string
 
 创建post_attachment脚手架 
 
rails generate scaffold post_attachment post_id:integer avatar:string

rake db:migrate
 
 在post.rb 
 
class Post < ActiveRecord::Base
   has_many :post_attachments
   accepts_nested_attributes_for :post_attachments
end
 
 在post_attachment.rb 
 
class PostAttachment < ActiveRecord::Base
   mount_uploader :avatar, AvatarUploader
   belongs_to :post
end
 
 在post_controller.rb 
 
def show
   @post_attachments = @post.post_attachments.all
end

def new
   @post = Post.new
   @post_attachment = @post.post_attachments.build
end

def create
   @post = Post.new(post_params)

   respond_to do |format|
     if @post.save
       params[:post_attachments]['avatar'].each do |a|
          @post_attachment = @post.post_attachments.create!(:avatar => a)
       end
       format.html { redirect_to @post, notice: 'Post was successfully created.' }
     else
       format.html { render action: 'new' }
     end
   end
 end

 private
   def post_params
      params.require(:post).permit(:title, post_attachments_attributes: [:id, :post_id, :avatar])
   end
 
 在views / posts / _form.html.erb 
 
<%= form_for(@post, :html => { :multipart => true }) do |f| %>
   <div class="field">
     <%= f.label :title %><br>
     <%= f.text_field :title %>
   </div>

   <%= f.fields_for :post_attachments do |p| %>
     <div class="field">
       <%= p.label :avatar %><br>
       <%= p.file_field :avatar, :multiple => true, name: "post_attachments[avatar][]" %>
     </div>
   <% end %>

   <div class="actions">
     <%= f.submit %>
   </div>
<% end %>
 
 编辑任何帖子的附件和附件列表。 在views / posts / show.html.erb 
 
<p id="notice"><%= notice %></p>

<p>
  <strong>Title:</strong>
  <%= @post.title %>
</p>

<% @post_attachments.each do |p| %>
  <%= image_tag p.avatar_url %>
  <%= link_to "Edit Attachment", edit_post_attachment_path(p) %>
<% end %>

<%= link_to 'Edit', edit_post_path(@post) %> |
<%= link_to 'Back', posts_path %>
 
 更新表单以编辑附件视图/ post_attachments / _form.html.erb 
 
<%= image_tag @post_attachment.avatar %>
<%= form_for(@post_attachment) do |f| %>
  <div class="field">
    <%= f.label :avatar %><br>
    <%= f.file_field :avatar %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>
 
 修改post_attachment_controller.rb中的更新方法 
 
def update
  respond_to do |format|
    if @post_attachment.update(post_attachment_params)
      format.html { redirect_to @post_attachment.post, notice: 'Post attachment was successfully updated.' }
    end 
  end
end
 
 在rails 3中，不需要定义强大的参数，并且可以在model和accept_nested_attribute中定义attribute_accessible来发布模型，因为在rails 4中不推荐使用属性。 
 
 为了编辑附件，我们不能一次修改所有的附件。 所以我们将一个接一个地替换附件，或者你可以根据你的规则进行修改。这里我只是向你展示如何更新任何附件。 

 
 
This is solution to upload multiple images using carrierwave in rails 4 from scratch
 
 
Or you can find working demo : Multiple Attachment Rails 4
 
 
To do just follow these steps.
 
rails new multiple_image_upload_carrierwave
 
In gem file
 
gem 'carrierwave'
bundle install
rails generate uploader Avatar 
 
Create post scaffold
 
rails generate scaffold post title:string
 
Create post_attachment scaffold
 
rails generate scaffold post_attachment post_id:integer avatar:string

rake db:migrate
 
In post.rb
 
class Post < ActiveRecord::Base
   has_many :post_attachments
   accepts_nested_attributes_for :post_attachments
end
 
In post_attachment.rb
 
class PostAttachment < ActiveRecord::Base
   mount_uploader :avatar, AvatarUploader
   belongs_to :post
end
 
In post_controller.rb
 
def show
   @post_attachments = @post.post_attachments.all
end

def new
   @post = Post.new
   @post_attachment = @post.post_attachments.build
end

def create
   @post = Post.new(post_params)

   respond_to do |format|
     if @post.save
       params[:post_attachments]['avatar'].each do |a|
          @post_attachment = @post.post_attachments.create!(:avatar => a)
       end
       format.html { redirect_to @post, notice: 'Post was successfully created.' }
     else
       format.html { render action: 'new' }
     end
   end
 end

 private
   def post_params
      params.require(:post).permit(:title, post_attachments_attributes: [:id, :post_id, :avatar])
   end
 
In views/posts/_form.html.erb
 
<%= form_for(@post, :html => { :multipart => true }) do |f| %>
   <div class="field">
     <%= f.label :title %><br>
     <%= f.text_field :title %>
   </div>

   <%= f.fields_for :post_attachments do |p| %>
     <div class="field">
       <%= p.label :avatar %><br>
       <%= p.file_field :avatar, :multiple => true, name: "post_attachments[avatar][]" %>
     </div>
   <% end %>

   <div class="actions">
     <%= f.submit %>
   </div>
<% end %>
 
To edit an attachment and list of attachment for any post. In views/posts/show.html.erb
 
<p id="notice"><%= notice %></p>

<p>
  <strong>Title:</strong>
  <%= @post.title %>
</p>

<% @post_attachments.each do |p| %>
  <%= image_tag p.avatar_url %>
  <%= link_to "Edit Attachment", edit_post_attachment_path(p) %>
<% end %>

<%= link_to 'Edit', edit_post_path(@post) %> |
<%= link_to 'Back', posts_path %>
 
Update form to edit an attachment views/post_attachments/_form.html.erb
 
<%= image_tag @post_attachment.avatar %>
<%= form_for(@post_attachment) do |f| %>
  <div class="field">
    <%= f.label :avatar %><br>
    <%= f.file_field :avatar %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>
 
Modify update method in post_attachment_controller.rb
 
def update
  respond_to do |format|
    if @post_attachment.update(post_attachment_params)
      format.html { redirect_to @post_attachment.post, notice: 'Post attachment was successfully updated.' }
    end 
  end
end
 
In rails 3 no need to define strong parameters and as you can define attribute_accessible in both the model and accept_nested_attribute to post model because attribute accessible is deprecated in rails 4.
 
For edit an attachment we cant modify all the attachments at a time. so we will replace attachment one by one, or you can modify as per your rule, Here I just show you how to update any attachment.