使用carrierwave上传多个文件

Question

如何修复错误＆＃34;没有将nil隐式转换为String＆＃34; ???

我的迁移（对于postgresql）：

class CreateFotos < ActiveRecord::Migration
  def change
    create_table :fotos do |t|
      t.json :path, null: false, default: '{}'
      t.string :title
      t.boolean :show
    end
  end
end

我的模特：

class Foto < ActiveRecord::Base
  mount_uploader :path, FotoUploader
end

我的控制器：

class FotoUploaderController < ApplicationController

  def create

    @foto = Foto.new(foto_params)

    if @foto.save!
      redirect_to root_path
    else
      flash[:notice] = "Didn't work"
      redirect_to foto_uploader_upload_path
    end
  end

  private
  def foto_params
    params.require(:foto).permit(:title, {path:[]}, :show)
  end

end

我的参数：

{"utf8"=>"✓",     "authenticity_token"=>"38YKuM3gibtrvr+Sd3C89chTh+kfEuVihbHyeUBxKDALxgSzZYhKL6zshevKjEtazXoiArm1YSryi4U+P4Vb3w==",
     "foto"=>{"path"=>[#<ActionDispatch::Http::UploadedFile:0x007f5e4e996318 @tempfile=#<Tempfile:/tmp/RackMultipart20160111-7835-ztbjyj.jpg>,
     @original_filename="3.jpg",
     @content_type="image/jpeg",
     @headers="Content-Disposition: form-data; name=\"foto[path][]\"; filename=\"3.jpg\"\r\nContent-Type: image/jpeg\r\n">],
     "title"=>"1",
     "show"=>"1"},
     "commit"=>"upload"}