Ruby on Rails“ NameError：未初始化的常量Mysql2 :: Client :: REMEMBER_OPTIONS”

Question

I am trying to learn web development with ruby on rails. I have been following a course on Lynda.com and my steps were as follows:

1. I installed Ruby + DevKit 2.4.4-1(x64)

2. I installed rails as in the command line as follows gem install rails --version 5.0.0

3. I installed MySQL version 5.7.21

4. I installed mysql2 gem as follows gem install mysql2

5. I installed Atom text editor

6. I created a new project rails new kudaweb -d mysql

7. I created the required databases in the MySQL shell

CREATE DATABASE kudaweb_development; and CREATE DATABASE kudaweb_test;

8. I then created a new user and granted all privileges as follows

GRANT ALL PRIVILEGES ON kudaweb_development.* TO 'rails_user'@'localhost' IDENTIFIED BY 'mypassword' and i did this for the test database as well

9. I configured the database.yml file as follows:

   default: &default adapter: mysql2 encoding: utf8 pool: 5 username: rails_user password: mypassword host: localhost

10. I ran the following code to check if I had correctly configured the database

rails db:schema:dump

and I got the following error

C:\\Users\\Dj K-Staxx\\Desktop\\RUBY\\kudaweb>rails db:schema:dump rails aborted! NameError: uninitialized constant Mysql2::Client::REMEMBER_OPTIONS bin/rails:4:in C:\\Users\\Dj K-Staxx\\Desktop\\RUBY\\kudaweb>rails db:schema:dump rails aborted! NameError: uninitialized constant Mysql2::Client::REMEMBER_OPTIONS bin/rails:4:in require' bin/rails:4:in <main>' Tasks: TOP => db:schema:dump

I have no idea how to resolve this. I have searched the internet for solutions but to no avail. I am using windows 7 64bit and for the mysql2 gem I am using version 0.5.0

Answer 1

Seems like there may be some config issue between your 0.5.0 gem and mysql. It may not have built correctly. see: https://github.com/brianmario/mysql2/issues/954

Option 1: try reverting to 0.4.9 or 0.4.10 gem

set your gemfile to:

# ./Gemfile
...
gem 'mysql2', '0.4.9'
...

Option 2: try to compile the gem locally with c-connector

You may need a local C-connector to properly build the gem locally. see: https://www.digitalgyan.org/how-to-install-ruby-on-rails-mysql2-gem-on-windows-10/

that may be as simple as downloading the appropriate files from MySQL: https://dev.mysql.com/downloads/connector/c/

In either scenario, you may benefit from a quick script to test out connection (to rule out Rails as the problem).

require 'mysql2'
client = Mysql2::Client.new(host: "localhost", username: "rails_user", password: "mypassword")

Answer 2

将Gemfile中的mysql2 gem更新为：

gem 'mysql2', '~> 0.5.2'