Defining custom exception in a module in Rails

Question

I've created a custom module (which currently only defines a new Exception class), and put it under lib/lib_th.rb

module LibTH
    module Error
        IDNotFound = Class.new
    end
end

I should not need to require/include the module in my code, as it should be automatically loaded, since it follows the conventional naming rules.

But when i try and raise the IDNotFound exception somewhere in my code:

res.size == 0 ? raise LibTH::Error::IDNotFound : res

I get the follwoing error:

SyntaxError (/Users/lrnz/code/ruby/corinna/app/models/treasure_hunt.rb:49: syntax error, unexpected tCONSTANT, expecting kDO or '{' or '('
  res.size == 0 ? raise LibTH::Error::IDNotFound : res
                             ^
/Users/lrnz/code/ruby/corinna/app/models/treasure_hunt.rb:49: syntax error, unexpected ':'
  res.size == 0 ? raise LibTH::Error::IDNotFound : res
                                                  ^):
app/controllers/treasure_hunts_controller.rb:50:in `show'

The strange thing is that I encounter no problems trying to raise the exception in script/console:

>> raise LibTH::Error::IDNotFound
LibTH::Error::IDNotFound: LibTH::Error::IDNotFound
from (irb):70

Thanks!

asymmetric · Accepted Answer · 2009-07-07 13:11:31Z

2

Nevermind, i solved the problem myself:

instead of using the if ? then : else statement, i expanded it into a:

raise LibTH::Error::IDNotFound if res.size == 0
res

It seems you can't use a constant value (as a class name) in the C-like if statement, thus the:

syntax error, unexpected tCONSTANT, expecting kDO or '{' or '('

Thanks asy!

answered Jul 7, 2009 at 13:11

asymmetric

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rue · Accepted Answer · 2011-05-16 14:34:52Z

2

The constant isn't a problem, you just have a syntax error with the raise. If you changed it to:

res.size == 0 ? (raise LibTH::Error::IDNotFound) : res

It would work. The form you corrected to is better anyway, though.

answered May 16, 2011 at 14:34

rue

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