如何通过一条救援声明尽快捕获所有异常
我知道如何捕捉异常,但我们所做的是在代码的可疑部分之后放置“救援”。 如果你有很多函数通过mysql2 gem发送一个查询到mysql并且你想要捕获它们的异常。 你可以做的一件事就是在他们每个人中加上一个“救援”声明。 但我只想通过一个救援声明来做到这一点。 因此,我在代码结束时加入了一个“救援”,并将所有代码放在“开始”和“结束”中,但它不起作用。
这里是我的代码,正如你看到的那样,在mysql查询中有一个问题,并且仅仅因为“rescue”是文件结尾,它不会捕获异常,但是当我把它放在那个查询之后它就起作用了。
require 'mysql2'
require 'colored'
begin
def log(string)
p "["+string.cyan+"]"
end
def err
p "["+"FAIL".red+"]"
end
def done
p "["+"DONE".red+"]"
end
class SqlClient
def initialize()
log "SqlClient/initialize"
puts "Host: n"
@host = gets.strip
puts "User: n"
@user = gets.strip
puts "Pass: n"
@pass = gets.strip
@client = Mysql2::Client.new(host: @host , username: @user , password: @pass)
end
def list_databases()
puts "We are listing your databases(not just projects) n n n "
@client.query("ELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA").each do |row|
p row["SCHEMA_NAME"]
end
puts "n n n"
end
end
rescue Mysql2::Error
err
abort
end
`query': You have an error in your SQL syntax; check the manual that corresponds to your
MySQL server version for the right syntax to use near 'ELECT SCHEMA_NAME FROM
INFORMATION_SCHEMA.SCHEMATA' at line 1 (Mysql2::Error)
我不是在寻找像这样的东西:
begin
# my code
rescue # this line is right after the code which is going to have problem and we catch it.
end
我正在寻找这样的东西:
begin
# first method
# second method
# thrid method
# rest of code and etc ...
# now this is end of file:
rescue
end
但正如你在我的代码中看到的那样,它不起作用。
更新:我在这里发现了一个类似的问题,似乎没有答案:| 也许这是一种红宝石的弱点。
如果你想看到任何错误,只需使用e
例如
begin
# your call to a method of Mysql2 gem. for example:
client = Mysql2::Client.new(:host => "localhost", :username => "root", etc...)
rescue => e
puts e.message
puts e.backtrace.inspect
end
为了捕获每个异常,您需要将每个方法调用与begin
rescue
end
。 当引发一个异常时,它会退出执行,所以它不会触发下一个方法。
为了抓住所有的错误,我想我会做这样的事情。 请记住,这是丑陋的,我建议你不要这样做,但是...如果你想尝试,也许尝试这样的事情:
all_errors = []
# first method you call
begin
# some error might happen here
first_response = Mysql2::Client.new(:host => "localhost", :username => "root", etc...)
rescue => e
all_errors << e
end
# second method you call
begin
# some error might happen here
second_response = Mysql2::Client.new(:host => "localhost", :username => "root", etc...)
rescue => e
all_errors << e
end
puts all_errors.inspect
经过快速搜索,我发现:(http://coderrr.wordpress.com/2008/11/07/the-simple-way-to-print-exceptions-in-ruby/)
# catch all exceptions (anything that derives from Exception)
begin
...
rescue Exception
puts $!, $@
end
您可以使用at_exit处理程序,它可以访问$!中的最后一个异常。
喜欢
at_exit {
puts "the exception that killed us is", $!
}
如果你想在发生异常的时候捕获异常(而不是被捕获后),你可以使用ruby的“调试模式”(在控制台出现消息时输出消息)或者ruby-debug看看有没有办法在异常情况下启动Ruby调试器?
只需将所有代码包装在:
begin
#yourcode
#as much as you want
rescue
end
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