In this article you ll learn how to use the rescue keyword in combination with begin to handle ruby exceptions the most effective way.
Ruby rescue exception type.
The match will succeed if the exception named in the rescue clause is the same as the type of the currently thrown exception or is a superclass of that exception.
Ryan davis s ruby quickref says without explanation.
That s because ruby uses exceptions for things other than errors.
Rescuing signalexception prevents the program from responding correctly to signals.
The code above will rescue every exception.
Become a better developer.
It places the keyword rescue after any code that would probably throw an exception.
For each rescue clause in the begin block ruby compares the raised exception against each of the parameters in turn.
How to handle an exception.
It will be unkillable except by kill 9.
It also uses them to handle messages from the operating system called signals if you ve ever pressed ctrl c to exit a program you ve used a signal.
Although libraries can define their own exception subclasses the list of built in exception subclasses on ruby 2 5 looks like this.
Or i will stab you.
The match will succeed if the exception named in the rescue clause is the same as the type of the currently thrown exception or is a superclass of that exception.
It ll break your program in weird ways.
Rescuing interrupt prevents the user from using ctrlc to exit the program.
While it may be tempting to rescue every child of the exception class it is generally considered bad practice due to the way the ruby exception hierarchy is structured.
You ve learned about errors in ruby basic exception handling the rescue begin keywords.
For each rescue clause in the begin block ruby compares the raised exception against each of the parameters in turn.
Ruby s exception handling mechanism is simple.
At its core every ruby exception stems from a built in exception class and includes a handful of built in methods but the most commonly used exception method is message.
Ruby does require some form of begin to appear before the rescue.
Ruby s exception hierarchy is used to differentiate between different types of errors while giving you the ability to rescue from a group of errors without specifying all of them.
This method can be used to retrieve a specific exception message from a raised exception object.
Exception is the root of ruby s exception hierarchy so when you rescue exception you rescue from everything including subclasses such as syntaxerror loaderror and interrupt.
The general syntax for the rescue statement is as follows.
