Question

我在Rails应用程序中遇到以下错误。你能帮我吗？

连接两个表时出现错误。用户想要使用表格。我正在尝试从单个表中管理经理ID和用户ID字段。

红宝石2.5.1p57（2018-03-29修订版63029）[x86_64-darwin17]

Rails 5.2.2

数据库设计和表 schema.rb：

ActiveRecord::Schema.define(version: 2019_02_24_160401) do

  create_table "projects", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.string "name"
    t.text "description"
    t.string "company"
    t.bigint "manager_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["manager_id"], name: "index_projects_on_manager_id"
  end

  create_table "users", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.string "email", default: "", null: false
    t.string "username", default: "", null: false
    t.string "fullname", default: ""
    t.bigint "manager"
    t.string "company", default: ""
    t.string "department", default: ""
    t.boolean "isadmin", default: false
    t.string "encrypted_password", default: "", null: false
    t.string "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["email"], name: "index_users_on_email", unique: true
    t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
  end

  add_foreign_key "projects", "users", column: "manager_id"
end

projects_controller.rb

class ProjectsController < ApplicationController
  before_action :set_project, only: [:show, :edit, :update, :destroy]
  before_action :find_users, only: [:index, :show, :new, :edit]
  # GET /projects
  # GET /projects.json
  def index
    @projects = Project.all
  end

  # GET /projects/1
  # GET /projects/1.json
  def show
  end

  # GET /projects/new
  def new
    @project = Project.new
  end

  # GET /projects/1/edit
  def edit
  end

  # POST /projects
  # POST /projects.json
  def create
    @project = Project.new(project_params)

    respond_to do |format|
      if @project.save
        format.html { redirect_to @project, notice: 'Project was successfully created.' }
        format.json { render :show, status: :created, location: @project }
      else
        format.html { render :new }
        format.json { render json: @project.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /projects/1
  # PATCH/PUT /projects/1.json
  def update
    respond_to do |format|
      if @project.update(project_params)
        format.html { redirect_to @project, notice: 'Project was successfully updated.' }
        format.json { render :show, status: :ok, location: @project }
      else
        format.html { render :edit }
        format.json { render json: @project.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /projects/1
  # DELETE /projects/1.json
  def destroy
    @project.destroy
    respond_to do |format|
      format.html { redirect_to projects_url, notice: 'Project was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_project
      @project = Project.find(params[:id])

    end

    def find_users
      @users = User.all.order('created_at desc')
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def project_params
      params.require(:project).permit(:name, :description, :user_id)
    end
end

模型文件夹中的模型文件 project.rb和user.rb

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
  has_many :projects
end

class Project < ApplicationRecord
  belongs_to :user
end

调用我的代码电子邮件专栏 index.html.erb

<p id="notice"><%= notice %></p>

<h1>Projects</h1>

<table>
  <thead>
    <tr>
      <th>Name</th>
      <th>Description</th>
      <th>Company</th>
      <th>Manager</th>
      <th colspan="3"></th>
    </tr>
  </thead>

  <tbody>
    <% @projects.each do |project| %>
      <tr>
        <td><%= project.name %></td>
        <td><%= project.description %></td>
        <td><%= project.company %></td>
        <td><%= project.user.email %></td>
        <td><%= link_to 'Show', project %></td>
        <td><%= link_to 'Edit', edit_project_path(project) %></td>
        <td><%= link_to 'Destroy', project, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

<%= link_to 'New Project', new_project_path %>

Answer 1

似乎数据没有在模式中草拟。 User和Manager是一样的东西吗？如果不是，则在user_id表中应该有一个Projects引用，否则，您必须添加将manager_id绑定到Users的适当关联，然后您才能拥有{ {1}}

Answer 2

您的#include <stdio.h> #include <ctype.h> #include <strings.h> #define NUM 50 #define STRINGS 100 #define OUTPUT 10 int main(void) { char str[STRINGS][NUM+1]; int answer[NUM+1] = {0}; int carry = 0, out_digits = OUTPUT; for(int i = 0; i < STRINGS; i++){ scanf("%s", str[i]); for(int j = NUM; j >=0; j--){ answer[j] += (str[i][j] - 48) + carry; if(answer[j] > 9){ carry = answer[j] / 10; answer[j] %= 10; }else{ carry = 0; } } } printf("--------------------------------------------------\r\n"); printf("%d",carry); for(int j = 0; j < OUTPUT-1; j++){ printf("%d",answer[j]); } printf("\r\n--------------------------------------------------"); return 0; }有一个Project，但没有名为manager_id的表，而是managers。因此，在项目与用户之间的关系中，它需要使用正确的密钥。

users

Answer 3

如果用户对于Project是可选的，则只需调用project.user&.email

Rails为nil：NilClass使用的未定义方法`email'

3 个答案: