Ruby Exceptions
Exceptions are a way of handling unexpected situations or errors that may occur during program execution. In Ruby, exceptions are objects that represent an error condition. When an exception is raised, Ruby begins looking for a place in the code that can handle it, otherwise the program terminates.
Syntax
begin
# Some code that may raise an exception
rescue [ExceptionType => e]
# Some code to handle the exception
ensure
# Some code that will be executed at the end, whether an exception occurred or not
end
Example
begin
# Open a file
file = File.open("non_existent_file.txt")
rescue Exception => e
# Handle the error by printing the error message
puts e.message
ensure
# Close the file, if it was opened successfully
file.close if file
end
Output
No such file or directory @ rb_sysopen - non_existent_file.txt
Explanation
In the above example, we try to open a file that does not exist. This operation raises an Errno::ENOENT
exception, which is caught and handled by the rescue
block. The ensure
block is executed at the end, regardless of whether an exception occurred or not.
Use
Exceptions are commonly used for error handling in Ruby programs. They can be used to catch and handle errors, or to signal an error condition in a function or method.
Important Points
- Exceptions in Ruby are objects that represent an error condition.
- Exceptions are raised when an unexpected situation or error occurs during program execution.
- The
rescue
block is used to catch and handle exceptions. - The
ensure
block is executed at the end, regardless of whether an exception occurred or not. - Ruby has a hierarchy of exception classes, with
StandardError
being the base class.
Summary
Exceptions are an important part of Ruby programming. They provide a way to handle unexpected situations or errors that may occur during program execution. By using the rescue
and ensure
blocks, we can gracefully handle exceptions and ensure that the program executes correctly.