我正在创建一个Rails博客，并使用 test samples 填充数据库，现在当我运行db:reset和db:migrate时，表格会在数据库中创建但是创建新文章或作者时显示以下错误。
Mysql2::Error: Field 'username' doesn't have a default value: INSERT INTO `authors` (`created_at`, `updated_at`) VALUES ('2013-09-29 05:30:43', '2013-09-29 05:30:43')
非常感谢帮助。
摘录来源
respond_to do |format|
**if @author.save**
format.html { redirect_to @author, notice: 'Author was successfully created.' }
format.json { render action: 'show', status: :created, location: @author }
else
if @author.save
Schema.rb
# encoding: UTF-8
# This file is auto-generated from the current state of the database. Instead
# of editing this file, please use the migrations feature of Active Record to
# incrementally modify your database, and then regenerate this schema definition.
#
# Note that this schema.rb definition is the authoritative source for your
# database schema. If you need to create the application database on another
# system, you should be using db:schema:load, not running all the migrations
# from scratch. The latter is a flawed and unsustainable approach (the more migrations
# you'll amass, the slower it'll run and the greater likelihood for issues).
#
# It's strongly recommended that you check this file into your version control system.
ActiveRecord::Schema.define(version: 20130928053429) do
create_table "articles", force: true do |t|
t.string "title"
t.text "body"
t.datetime "created_at"
t.datetime "updated_at"
t.string "image_file_name"
t.string "image_content_type"
t.integer "image_file_size"
t.datetime "image_updated_at"
end
create_table "authors", force: true do |t|
t.string "username", null: false
t.string "email"
t.string "crypted_password"
t.string "salt"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "comments", force: true do |t|
t.string "author_name"
t.text "body"
t.integer "article_id"
t.datetime "created_at"
t.datetime "updated_at"
end
add_index "comments", ["article_id"], name: "index_comments_on_article_id", using: :btree
create_table "pages", force: true do |t|
t.string "title"
t.text "body"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "taggings", force: true do |t|
t.integer "tag_id"
t.integer "article_id"
t.datetime "created_at"
t.datetime "updated_at"
end
add_index "taggings", ["article_id"], name: "index_taggings_on_article_id", using: :btree
add_index "taggings", ["tag_id"], name: "index_taggings_on_tag_id", using: :btree
create_table "tags", force: true do |t|
t.string "name"
t.datetime "created_at"
t.datetime "updated_at"
end
end
作者控制器
class AuthorsController < ApplicationController
before_action :set_author, only: [:show, :edit, :update, :destroy]
def zero_authors_or_authenticated
unless Author.count == 0 || current_user
redirect_to root_path
false
end
end
# GET /authors
# GET /authors.json
def index
@authors = Author.all
end
# GET /authors/1
# GET /authors/1.json
def show
end
# GET /authors/new
def new
@author = Author.new
end
# GET /authors/1/edit
def edit
end
# POST /authors
# POST /authors.json
def create
@author = Author.new(author_params)
respond_to do |format|
if @author.save
format.html { redirect_to @author, notice: 'Author was successfully created.' }
format.json { render action: 'show', status: :created, location: @author }
else
format.html { render action: 'new' }
format.json { render json: @author.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /authors/1
# PATCH/PUT /authors/1.json
def update
respond_to do |format|
if @author.update(author_params)
format.html { redirect_to @author, notice: 'Author was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: 'edit' }
format.json { render json: @author.errors, status: :unprocessable_entity }
end
end
end
# DELETE /authors/1
# DELETE /authors/1.json
def destroy
@author.destroy
respond_to do |format|
format.html { redirect_to authors_url }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_author
@author = Author.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def author_params
params.require(:author).permit(:username, :email, :password, :password_confirmation)
end
end
尝试使用Rails控制台创建新作者时，会弹出以下错误。
Author.new(username: 'ajay', email: 'ajkumar_25@yahoo.com', password: '12345', password_confirmation: '12345').save
WARNING: Can't mass-assign protected attributes for Author: username, email, password, password_confirmation
(0.3ms) BEGIN
ActiveRecord::StatementInvalid: Mysql2::Error: Field 'username' doesn't have a default value: INSERT INTO `authors` (`created_at`, `updated_at`) VALUES ('2013-09-29 06:00:23', '2013-09-29 06:00:23')
from /home/aj/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:286:in `query'
SQL (0.7ms) INSERT INTO `authors` (`created_at`, `updated_at`) VALUES ('2013-09-29 06:00:23', '2013-09-29 06:00:23')
Mysql2::Error: Field 'username' doesn't have a default value: INSERT INTO `authors` (`created_at`, `updated_at`) VALUES ('2013-09-29 06:00:23', '2013-09-29 06:00:23')
(0.2ms) ROLLBACK
答案 0 :(得分：3)
在schema.rb中，它表示不允许username为空：
t.string "username", null: false
在错误消息中，您可以看到未设置用户名，因此数据库拒绝新行。
INSERT INTO `authors` (`created_at`, `updated_at`) VALUES ('2013-09-29 05:30:43', '2013-09-29 05:30:43')
您应该确保设置username。
[更新]以回应原始问题中的更新：
现在你要看的关键是这一行：
WARNING: Can't mass-assign protected attributes for Author: username, email, password, password_confirmation
您需要阅读attr_accessible和attr_protected。您可能需要在Author模型中使用此类内容。
attr_accessible :username, :email, :password, :password_confirmation
答案 1 :(得分：0)
在尝试创建新的“作者”行时，显然缺少“用户名”字段，架构被配置为“非空”。
在某些时候，应该设置@ authors.username。这可以通过显式调用来实现 @ authors.username = params [...或批量作业。
答案 2 :(得分：0)
看起来您需要在模型上设置attr_accessible声明：
class Author < ApplicationController
attr_accessible :username, :email # etc
end