Question

我正在尝试使用我的rails应用程序中的carrierwave gem实现上传图像，但是当我按下表单的提交按钮时，我发现以下错误：“无法将nil转换为字符串”

应用程序跟踪：

app/controllers/uploads_controller.rb:48:in `new'
app/controllers/uploads_controller.rb:48:in `create'

请求：

{"utf8"=>"✓",
"authenticity_token"=>"VsgoOE/BQwwT0aQRRMO22kxdPgC/BS2H/CnHVBi4Cfw=",
"upload"=>{"name"=>"aaa",
"description"=>"aa",
"image"=>[#<ActionDispatch::Http::UploadedFile:0x508a8b0 @original_filename="c1147374806dce0ec967015c041fec3b.jpg",
@content_type="image/jpeg",
@headers="Content-Disposition: form-data; name=\"upload[image][]\"; filename=\"c1147374806dce0ec967015c041fec3b.jpg\"\r\nContent-Type: image/jpeg\r\n",
@tempfile=#<File:C:/Users/user/AppData/Local/Temp/RackMultipart20150621-5356-1gm0atx>>]},
"commit"=>"Upload"}

上传模型：

class Upload < ActiveRecord::Base
    validates_presence_of :user_id, :image
    attr_accessible :name, :description, :image
    mount_uploader :image, ImageUploader
end

上传控制器：

class UploadsController < ApplicationController
    before_filter :signed_in_user

    def index
    (...)
    end

    def show
    (...)
    end

    def new
        @upload = Upload.new
        respond_to do |format|
            format.html # new.html.erb
            format.json { render json: @upload }
        end
    end

    def edit
        (...)
    end

    def create
        @upload =  Upload.new(params[:upload])
        @upload.user_id = current_user.id
        respond_to do |format|
            if @upload.save

                format.html { redirect_to @upload, notice: 'Image was uploaded.' }
                format.json { render json: @upload, status: :created, location: @upload }

            else
                format.html { render action: "new" }
                format.json { render json: @upload.errors, status: :unprocessable_entity }
            end
        end
    end

    def update
        (...)
    end

    def destroy
        (...)
    end
end

上传表单（uploads / _form.html.erb）：

<%= form_for @upload, :html => {:id => "upload_form", :multipart => true} do |f| %>
    <div class="field">
        <%= f.text_field :name, placeholder: 'Title' %>
    </div>
    <div class="field">
        <%= f.text_field :description, placeholder: 'Description' %>
    </div>
    <%= f.file_field :image, multiple: true %>
    <div class="actions">
        <%= f.submit "Upload" %>
    </div>
<% end %>

carrierwave uploader：

class ImageUploader < CarrierWave::Uploader::Base
    storage :file

    def store_dir
        "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
    end
end

上传模式：

create_table "uploads", :force => true do |t|
    t.string   "name"
    t.string   "description"
    t.integer  "user_id"
    t.datetime "created_at",  :null => false
    t.datetime "updated_at",  :null => false
    t.string   "image"
end

carrierwave保存图片的目录：

public
    uploads
        upload
            image
                1
                ...

第48行引用的应用程序跟踪是@upload = Upload.new(params[:upload])。

如何解决此问题？我无法确定上传为nil的原因。有人能以正确的方式把我带来吗？

一些细节：OS Win7 Pro，Rails v.3.2.21，Carrierwave v.0.10.0，IDE Rubymine v.7.1.2

编辑1 ：根据@sreena的建议，我从上传切换到图像，现在这是请求消息：

Parameters: {"utf8"=>"✓",
"authenticity_token"=>"G1zpdyCbXRJYqAR5m5hscMjQOry85KN7toNhJznOFok=",
"upload"=>{"name"=>"titolo", "description"=>"descrizione",
"image"=>[#<ActionDispatch::Http::UploadedFile:0x534aef0 @original_filename="2.jpg", 
@content_type="image/jpeg", @headers="Content-Disposition: form-data;
name=\"upload[image][]\"; filename=\"2.jpg\"\r\nContent-Type: image/jpeg\r\n",
@tempfile=#<File:C:/Users/user/AppData/Local/Temp/RackMultipart20150624-4180-14oypoq>>]},
"commit"=>"Upload"}

按下提交按钮后，现在我从表单"Image can't be blank"中重新提出了另一个错误。

Answer 1

你应该在控制器中传递create参数

@upload = Upload.new（params [：image]）

，应该是图片不上传

Answer 2

in your UploadsContoller page add this function def upload_params params.require(:upload).permit(:image,:name,:description) end

and in def create add like this

def create @upload = Upload.new(upload_params) @upload.user_id = current_user.id respond_to do |format| if @upload.save

            format.html { redirect_to @upload, notice: 'Image was uploaded.' }
            format.json { render json: @upload, status: :created, location: @upload }

        else
            format.html { render action: "new" }
            format.json { render json: @upload.errors, status: :unprocessable_entity }
        end
    end
end

Answer 3

最后我解决了这个问题。我只是按以下方式更改create方法

def create
    @upload =  current_user.uploads.build(params[:upload])
    @upload.image = params[:upload]["image"]
    respond_to do |format|
    if @upload.save

        format.html { redirect_to @upload, notice: 'Image was uploaded.' }
        format.json { render json: @upload, status: :created, location: @upload }

    else
        format.html { render action: "new" }
        format.json { render json: @upload.errors, status: :unprocessable_entity }
    end
end

Rails 3和carrierwave：无法将nil转换为字符串

3 个答案: