ruby exception handling

About this article

In job change activities, I sometimes described exception handling in technical issues, but I have never experienced it before, so it is an output

What is exception handling?


#Specify code to detect problems when running a program
#Write code that is likely to cause an error


#Describe how to respond when a problem is detected


Raise an exception

With the following code, 100 / 0 cannot be executed, so processing will stop at ʻanswer = 100 / number. ZeroDivisionError` is the corresponding error, and describe the processing you want to perform when this exception occurs.

number = 0
answer = 20 / num
puts answer
puts 2

=>`/': divided by 0 (ZeroDivisionError)
	from Main.rb:4:in `<main>'

Exception handling

If you write as follows, the exception will normally occur at 100/0, so the processing will stop, but since the processing in rescue is performed, the processing will be executed to the end.

puts 1
    #Write the code you want to detect
    number = 0
    answer = 20 / num
    puts answer
rescue ZeroDivisionError => e
   #Describe the process you want to perform when ZeroDivisionError occurs (register an exception handler)
    p e
    puts 2

#<ZeroDivisionError: divided by 0>

What is e?

It is a ZeroDivisionError object (variable) that stores the details of the exception that occurred. In other words, if you output this, you can understand why the error occurred.

How to output

Objects have various messages and can retrieve necessary information as shown below.

p e

puts e.message

p e.backtrace

#<ZeroDivisionError: divided by 0>

divided by 0

["Main.rb:4:in `/'", "Main.rb:4:in `<main>'"]

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