Ruby Exception Handling

Exception is unreliable condition which are occurred during the program execution. This unwanted condition are disturbed the program execution process and abnormally terminate program execution. So this are not good to programmer and user perspective.

Ruby programming are providing a controlling mechanism which are capable to handle unwanted situation. And defining rules which are handle custom and system exception this is called Exception handling. Let see an example.

puts "Running Code"
#Suppose error are occurred
raise 'Getting Error'  

puts "End Code"

Output

Running Code
exception.rb:3:in `<main>': Getting Error (RuntimeError)

raise method are create an exception of RuntimeError type this method are exist in kernel module. And when error are occurred and not handling this error then the program are terminated. Let see an example of, how to control exception in Ruby programming.

def checkTest(parms)
  begin  
      puts 'Check Test' 

      #define of custom test case condition of exception 
      if parms.class== NilClass or  parms.class == String
        raise  ArgumentError,'ArgumentError has occured.'
      end  
        
        #work when parms are not zero
      puts "Result : #{10/parms}";

      puts 'All Test Case Valid'  

  rescue  ArgumentError
      puts 'Invalid Value are pass'

  rescue  ZeroDivisionError
      puts 'Zero By Zero Error'
  end

  puts "-----------"
end

checkTest(2)
checkTest(nil)
checkTest("Two")
checkTest(0)

Output

Check Test
Result : 5
All Test Case Valid
-----------
Check Test
Invalid Value are pass
-----------
Check Test
Invalid Value are pass
-----------
Check Test
Zero By Zero Error
-----------

In this program is capable to handle three type of exception. First is given argument is form of an nil object, when argument of method is form of String, and when number is divide by zero.

Predefined Exception List

Custom Exception Handling

#implement custom exception 
def my_exception
  begin  
    raise 'A simple exception'  
  rescue StandardError => e  
    puts e.backtrace.inspect 
    puts e.message  
     
  end  
end     
  
# calling method 
my_exception

["test.rb:4:in `exception'", "test.rb:13:in `<main>'"]
A simple exception