如何检查mysql连接

Question

我想在执行查询之前检查数据库是否存在连接。

但是，当我写if mysql_connection ...那么它mysql_connection经过两次：

def mysql_connection 
    puts "mysql_connection 1" 

    read_config_file 
    @connexion = Mysql2::Client.new(:host => @conf['host'], :username => @conf['user'], :password => @conf['password'], :database=> @conf['base'], :port => @conf['port']) 
end 

# USER QUERY MYSQL 
def mysql_select_user(value) 
    puts "select" 

    # if mysql_connection then 
    p = mysql_connection.query("select #{value} from User") 
    p.each do |f| 
     puts "value : #{f}" 
     mysql_close 
    end 
    # else 
    # end 
end 

Answer 1

使用Mysql2::Client#ping方法（从文档：http://www.rubydoc.info/gems/mysql2/0.3.13/Mysql2/Client#ping-instance_method）