# Exception Handiling

**URL:** <https://www.ruby-forum.com/t/exception-handiling/114221>\
**Category:** Rails\
**Created:** [September 10, 2007, 6:58am UTC](https://www.ruby-forum.com/t/exception-handiling/114221 "2007-09-10T06:58:12Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![advait](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e19adc/32.png) [@advait](https://www.ruby-forum.com/u/advait)\
**Post date:** [September 10, 2007, 6:58am UTC](https://www.ruby-forum.com/t/exception-handiling/114221/1 "2007-09-10T06:58:12Z")

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Hello,

I have a basic idea of what an exception is but I am not able to  
understand it so that I can make use of it in my application’s.  
If possible please try and help me out with the basic of exception and  
its use.

It would also be great, if any one of you could give me certain links on  
exceptions which would help me understand its concepts better.

Thank You

---

<div class="post-metadata">

**Author:** ![advait](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e19adc/32.png) [@advait](https://www.ruby-forum.com/u/advait)\
**Post date:** [September 10, 2007, 7:42am UTC](https://www.ruby-forum.com/t/exception-handiling/114221/2 "2007-09-10T07:42:31Z")

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typical exception look as below:

begin  
raise Exception.new("")  
rescue Exception =\> x  
puts x.message  
rescue  
puts "an error has occured  
end

if an exception is raised then all code after is skipped up to the  
rescue which rescues the program.

if an exception is called outside a begin block the exception will be  
raised up the stack until a rescue block is found. classes may declare a  
rescue\_method that wild catch exceptions raised by any method in the  
class.

Exceptions are meant to be use when errors occur that directly impact  
the program. For instance if a configuration file is missing that will  
throw an exception were as if the file is part of a user input and isn’t  
expected to be there then normal error handling would be appropriate.

---

<div class="post-metadata">

**Author:** ![advait](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e19adc/32.png) [@advait](https://www.ruby-forum.com/u/advait)\
**Post date:** [September 10, 2007, 9:26am UTC](https://www.ruby-forum.com/t/exception-handiling/114221/3 "2007-09-10T09:26:11Z")

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> It would also be great, if any one of you could give me certain links on  
> exceptions which would help me understand its concepts better.

[http://ruby.activeventure.com/programmingruby/book/tut\_exceptions.html](http://ruby.activeventure.com/programmingruby/book/tut_exceptions.html)

…some arbitrary simple example i can think of; say you have a  
ActiveRecord model Item with records in the db ranging from 1-100, and u  
search for #101:

class ItemController

def example  
Item.find(101) # this raises an exception  
rescue ActiveRecord::RecordNotFound # this will catch this specific  
exception  
flash[:notice]=“the record was not found!”  
redirect\_to :other\_action  
end

end

in this example instead of the app crashing since no record was found,  
we send a message to the user via the other\_action+flash message.

the syntax of the rescue clauses are pretty simple; if you have the name  
of the Exception you can rescue that SPECIFIC exception like the example  
above.

if you want to catch any old exception (doesn’t matter what the reason  
is) you can just write “rescue” without anything appended.

you can also do multiple resuces, with each rescue rescuing a certain  
exception type.

hope the link helps out too.  
good luck!

[http://ruby.activeventure.com/programmingruby/book/tut\_exceptions.html](http://ruby.activeventure.com/programmingruby/book/tut_exceptions.html)