如何檢查mysql連接

Question

我想在執行查詢之前檢查數據庫是否存在連接。

但是，當我寫if mysql_connection ...那麼它mysql_connection經過兩次：

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（從文檔：http://www.rubydoc.info/gems/mysql2/0.3.13/Mysql2/Client#ping-instance_method）