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How to Handle Exceptions in Ruby
Exceptions in programming are errors that occur at runtime. They are hard to handle in an effective manner, but it is important to handle them, else they halt the program execution.
Some of the common exceptions that one can encounter are −
trying to open a file that is not there,
dividing the number with zero,
running out of memory etc.
Now let's take a couple of examples to demonstrate how exceptions halt the execution of a Ruby program.
Example 1
Consider the code shown below.
taking two integer value
$First = 10;
$Second = 0;
# divide by zero error
$Third = $First / $Second;
puts "The Result is: #{$Third}"In this program, we are having two integers and we are dividing them, where the second integer is a zero, which will result in an exception.
Output
It will produce the following output.
main.rb:1:in `': undefined local variable or method `value' for main:Object (NameError)
We saw that in the above example, we encountered an exception that occurred due to some error in the code, but we can even create our own exceptions with the help of the raise keyword.
Example 2
Consider the code shown below.
# defining a method def raising_exception puts 'Before Exception!' # using raise to create exception raise 'Exception Created' puts 'After Exception Arise' end # Calling the method raising_exception
In this program, we are creating a new exception and then we are having two logs in the method where the exception is raised.
It should be noted that once an exception is encountered, there won't be any logs that will be printed after it, as the program comes to a halt.
Output
It will produce the following output.
Before Exception! Traceback (most recent call last): 1: from main.rb:13:in `<main>' main.rb:7:in `raising_exception': Exception Created (RuntimeError)
Example 3
Now that we have seen how an exception works and how we can create an exception for ourselves, let's see how we can handle that exception through an example. Consider the code shown below
# defining a method def rescue_from_raise begin puts 'Before Exception!' # using raise to create an exception raise 'Exception Created!' puts 'After Exception!' # using Rescue method rescue puts 'Saved!' end puts 'Outside!' end # calling method rescue_from_raise
Output
It will produce the following output.
Before Exception! Saved! Outside!
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