Rails 4如何使用carrierwave验证嵌套属性的数量（多个图像/图片）

Question

我是 stackoverflow 和 Rails 的新手。我有三个模型，User、Post、post_attachment（创建 post_attachment 脚手架）。 我想做的是，每个帖子（帖子标题，内容，图片）用户最多只能上传5张图片（我的意思是每个帖子）。我参考了这个article来实现多张图片和基本上遵循这个代码。我还发现这个article 来验证nested_attributes 但只有图片验证（nested_attributes）不起作用。任何想法，将不胜感激。谢谢。

用户.rb：

class User < ActiveRecord::Base
   has_many :posts, dependent: :destroy 
end

Post.rb：

class Post < ActiveRecord::Base
   belongs_to :user
   has_many :post_attachments
   accepts_nested_attributes_for :post_attachments,allow_destroy: true, reject_if: :all_blank
end

Post_attachment.rb：

class PostAttachment < ActiveRecord::Base
   mount_uploader :picture,PictureUploader 
   belongs_to :post
end

Post_controller.rb：

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

def show
   @post_attachments = @post.post_attachments.all
end

def create
   @post = current_user.posts.build(post_params)

  if @post.save
    params[:post_attachments]['picture'].each do |a|
          @post_attachment = @post.post_attachments.create!(:picture => a, :post_id => @post.id)
    end
    redirect_to @post, notice: "Post Saved" 
   else
     render 'new'
  end
end

private

def post_params
   params.require(:post).permit(:title,:content,:user_id,post_attachments_attributes: [:id, :post_id, :picture, :_destroy])
end

Answer 1

您可以将条件放在create 和edit 方法之前，也可以放在edit.html.erb 中。 比如如果你想保存最多 5 张照片，你可以使用

def create
  @post = current_user.posts.build(post_params)

  if @post.save
    ##@post_attachments = PostAttachment.find_by_post_id(@post.id) --> this can be use in edit
    ##if params[:post_attachments]['picture'].length+ @post_attachment.length <= 5
     if params[:post_attachments]['picture'].length <= 5
       params[:post_attachments]['picture'].each do |a|
          @post_attachment = @post.post_attachments.create!(:picture => a, :post_id => @post.id)
       end
     elsif params[:post_attachments]['picture'].length > 5
       flash[:error] = 'Your message'
       redirect_to YOUR_PATH
       return false
     end
     redirect_to @post, notice: "Post Saved" 
  else
   if params[:post_attachments]['picture'].length > 5
      @post.errors[:base] << "Maximuim 5 messages/pictures."
   end
   render 'new'
 end
end

您也可以在编辑帖子时签入视图。

<% if @post_attachments.length <= 5 %>
   <%= f.file_field %>
<% end %>