I'm trying to rescue the exception that ruby raises when you try to use the same address twice in a bind statement. The documentation is not very helpful.
Here's what I want:
require 'socket'
s = UDPSocket.new(Socket::AF_INET)
begin
s.bind address,port
rescue #Address_in_use => e
#code
end
rescue without an explicit Exception class only rescues StandardError and its subclasses. You should do the following:
rescue Errno::EADDRINUSE => ex
#code
end
Related
Rubocop doesn't seem to like how I am handling my error. What should I do?
Lint/UselessAssignment: Useless assignment to variable - e.
rescue *exceptions_list => e
It is for the piece of code below:
def get_request(url_args = {})
http_connection(url_builder(url_args[:url], url_args[:page]))
rescue *exceptions_list => e
raise "#{e.message}"
end
The *exceptions_list that you see there is defined in a private method:
private
def exceptions_list
[
Net::HTTPBadResponse,
Net::HTTPHeaderSyntaxError,
Net::ProtocolError,
Errno::ECONNRESET,
Errno::EINVAL,
Timeout::Error,
EOFError,
SocketError
]
end
To avoid the rescue line being too long.
Question:
Having => e is pretty standard for error handling no? What should I do?
Thank you very much in advance! =)
Your example does not give Lint/UselessAssignment from rubocop, not at least with version 0.55.0
The UselessAssignment usually comes from something like this:
def do_things
..
rescue *exception_list => e # Useless assignment, e is never used in the block below.
puts "it failed :("
end
To fix this, you can remove the assignment if you're not using the raised exception for anything:
def do_things
..
rescue *exception_list
puts "it failed and i don't care why :D"
end
I'm trying to understand how errors propogate between classes in Ruby. I have this so far:
class User
def charge
puts "charging order soon"
raise RuntimeError.new("This is a runtime error")
rescue ArgumentError
puts "should never gets here"
end
end
class Runner
def run
begin
User.new.charge
rescue RuntimeError => e
puts e.message
end
end
end
Runner.new.run
When I run this, I get this which seems right:
$ ruby errors.rb
charging order soon
This is a runtime error
Inside runner, can I rescue from the RuntimeError with a specific message? If I have multiple RuntimeErrors being raised around my application, is there any way for the Runner's rescue clause to be raised only for RuntimeErrors with specific messages?
See https://stackoverflow.com/a/23771227/2981429
If you call raise inside a rescue block, the last raised exception will be re-raised.
In your exception block, you can check the message and choose to re-raise or not:
begin
User.new.charge
rescue RuntimeError => e
case e.message
when "This is a runtime error"
# put your handler code here
else
raise # re-raise the last exception
end
end
However if it's your goal to solely rescue errors that you yourself raise manually, then it's probably easier to define a custom error class instead:
class MyError < StandardError; end
Then instead of raise RuntimeError.new("message") use raise MyError.new("message"), and rescue it normally:
begin
User.new.charge
rescue MyError => e
# handler
end
This way you don't have to worry about your rescues interfering with the built-in exceptions.
Is there a way, within a rescue clause, to put all the errors into an array and call them from there, if the error is in the array?
For example:
FATAL_ERRORS = %w(Mechanize::ResponseCodeError RestClient::ServiceUnavailable OpenSSL::SSL::SSLError RestClient::BadGateway)
begin
# Do some cool stuff
rescue FATAL_ERRORS => e
puts "Exiting #{e}"
What I've tried:
I've tried grabbing the error from the current thread:
FATAL_ERRORS = Thread.current[:errors] ||= %w(Mechanize::ResponseCodeError RestClient::ServiceUnavailable OpenSSL::SSL::SSLError RestClient::BadGateway)
begin
# Do some cool stuff
rescue FATAL_ERRORS => e
puts "Exiting #{e}"
Also I've tried the splat operator:
FATAL_ERRORS = %w(Mechanize::ResponseCodeError RestClient::ServiceUnavailable OpenSSL::SSL::SSLError RestClient::BadGateway)
begin
# Do some cool stuff
rescue *FATAL_ERRORS => e
puts "Exiting #{e}"
Both the splat and the thread produce the following exception:
rescue in <main>': class or module required for rescue clause (TypeError)
How can I successfully rescue multiple errors without putting them all on the rescue line and making it look bad?
splat does work. Problem is in the way you are making FATAL_ERRORS constant. With %w notation, it converts value as string:
%w(Mechanize::ResponseCodeError)
=> ["Mechanize::ResponseCodeError"] # Note the string value instead of class constant.
Try
FATAL_ERRORS = [Mechanize::ResponseCodeError, RestClient::ServiceUnavailable, OpenSSL::SSL::SSLError, RestClient::BadGateway]
Is there any way with Rspec to set an expectation for an exception that gets caught? I want to verify that MyException gets raised, but since I am catching the exception Rspec does not appear to know it ever happened.
begin
if success
do good stuff
else
raise MyException.new()
end
rescue MyException => e
clean up
end
I've tried a few things like the following without success. MyException.should_receive(:new) and
Kernel.should_receive(:raise).with(MyException)
You could test the behavior of the rescue block instead of checking for the exception:
class Test
def my_method
if success
# do good stuff
else
raise MyException.new()
end
rescue MyException => e
clean_up
end
end
describe Test do
it "should clean up when unsuccessful" do
subject.stub(:success) { false }
subject.should_receive(:clean_up)
subject.my_method
end
end
I figured out how to do what I needed.
class MyClass
def my_method
begin
if success
do good stuff
else
raise MyException.new
end
rescue MyException => e
# clean up
end
end
end
describe MyClass do
it "Expects caught exception" do
my_instance = MyClass.new()
my_instance.should_receive(:raise).with(any_instance_of(MyException))
my_instance.my_method()
end
end
Thanks for your other suggestions.
I would do as below:
RSpec.describe "matching error message with string" do
it "matches the error message" do
expect { raise StandardError, 'this message exactly'}.
to raise_error('this message exactly')
end
end
copied verbatim from Rspec Documentation
I know how to catch the exceptions but what we do is to put "rescue" after a suspicious section of a code. what if you had a lot functions sending a query to mysql through mysql2 gem and you want to catch their exceptions. One thing you can do is to put a "rescue" statement in each of them. but i want to do that just by one rescue statement. So I put a "rescue" in end of code and put all of code in a "begin" and "end" but it didn't work.
Here is my code and as you see there is a problem in mysql query and just because of "rescue" being end of file, it doesn't catch the exception but when I put it after that query it works.
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)
I'm not looking for something like:
begin
# my code
rescue # this line is right after the code which is going to have problem and we catch it.
end
I'm looking for something like this:
begin
# first method
# second method
# thrid method
# rest of code and etc ...
# now this is end of file:
rescue
end
but as you saw in my code, it didn't work.
UPDATE: I found a similar question here and it seems there will be no answer :| maybe this is a sort of ruby Weakness.
if you want to see ANY error just use e for example
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
In order to catch every exception you'd need to wrap each method call with a begin rescue end. When an exception is raised it bails out of the execution so it wouldn't hit the next methods.
To catch all errors I guess I'd do something like this. Keep in mind, this is ugly and I'd recommend for you NOT to do this, but... if you want to try, maybe try something like this:
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
After a quick search I've found: (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
You could use an at_exit handler, which has access to the last exception in $!
like
at_exit {
puts "the exception that killed us is", $!
}
If you want to catch Exceptions "as soon as they occur" (not after they're caught) you could use ruby's "debug mode" (which outputs messages when they occur to the console) or ruby-debug see Is there any way to start the Ruby debugger on exception?
Just wrap all your code in:
begin
#yourcode
#as much as you want
rescue
end
Nobody seemed to notice it but using rescue without a class will catch all StandardError and there are so much more.
If you want to catch ALL exceptions you need to do
begin
# your code where you call SqlClient.new etc
rescue Exception => e
puts "error raised"
puts [e, e.backtrace].flatten.join("\n")
end
List of all error classes:
Exception
NoMemoryError
ScriptError
LoadError
NotImplementedError
SyntaxError
SignalException
Interrupt
StandardError
ArgumentError
IOError
EOFError
IndexError
LocalJumpError
NameError
NoMethodError
RangeError
FloatDomainError
RegexpError
RuntimeError
SecurityError
SystemCallError
SystemStackError
ThreadError
TypeError
ZeroDivisionError
SystemExit
fatal
have you tried adding an at_exit method in your class? This would allow you to do something when ruby is exiting. like in this article.
Ruby at_exit
or
From Ruby 2.0 API Docs
However beware of cleverly rescuing from an exception!
You'll start pulling your hair out down the road (or another dev will) when you try to figure out why your code isn't failing when it should be failing. I prefer to fail massively with a bright shiny sign saying the code failed here! hehe.
Good luck!