exceptions

[Simon Kitching]

Hi,

I'm puzzled about how to associate custom information with an Exception
class I am throwing.

In Java, I would do this

MyException e = new MyException("foo", "bar", "baz");
e.doSomething();
e.setWidget(widget);
// now e is all set up, so throw it
throw e;

Can this sort of thing be done in Ruby??

Thanks,

Simon

[Ryan Pavlik]

On Tue, 4 Nov 2003 08:49:48 +0900
Simon Kitching <simon@ecnetwork.co.nz> wrote:

> Hi,
>
> I'm puzzled about how to associate custom information with an Exception
> class I am throwing.
>
> In Java, I would do this
>
> MyException e = new MyException("foo", "bar", "baz");
> e.doSomething();
> e.setWidget(widget);
> // now e is all set up, so throw it
> throw e;
>
> Can this sort of thing be done in Ruby??

Yes, just subclass Exception and treat it like a normal class (since
it is a normal class). I use this as some evil magic to implement a
few things.

--
Ryan Pavlik <rpav@mephle.com>

"Yeah, I mean what're the odds of those two brain cells bumping into
each other admist all that emptiness?" - 8BT

[Joel VanderWerf]

Simon Kitching wrote:

> Hi,
>
> I'm puzzled about how to associate custom information with an Exception
> class I am throwing.
>
> In Java, I would do this
>
> MyException e = new MyException("foo", "bar", "baz");
> e.doSomething();
> e.setWidget(widget);
> // now e is all set up, so throw it
> throw e;
>
> Can this sort of thing be done in Ruby??

Yep:

class MyException < Exception
def initialize(*args); @args = args; end
def doSomething; end
def setWidget(widget); @widget = widget; end
end

e = MyException.new("foo", "bar", "baz")
e.doSomething
e.setWidget("widget")
raise e

[Ara.T.Howard]

On Tue, 4 Nov 2003, Simon Kitching wrote:

> Hi,
>
> I'm puzzled about how to associate custom information with an Exception
> class I am throwing.
>
> In Java, I would do this
>
> MyException e = new MyException("foo", "bar", "baz");
> e.doSomething();
> e.setWidget(widget);
> // now e is all set up, so throw it
> throw e;
>
> Can this sort of thing be done in Ruby??

something like this?

irb(main):001:0> class MyException < Exception; def method(arg); @arg = arg; end; end
=> nil

irb(main):002:0> e = MyException.new 'foo bar baz'
=> #<MyException: foo bar baz>

irb(main):003:0> e.method 42
=> nil

irb(main):004:0> raise e
(irb):4:in `irb_binding': foo bar baz (MyException)
from /data/ruby-1.8.0//lib/ruby/1.8/irb/workspace.rb:52:in `irb_binding'
from /data/ruby-1.8.0//lib/ruby/1.8/irb/workspace.rb:52

-a
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[Simon Kitching]

On Tue, 2003-11-04 at 12:58, Joel VanderWerf wrote:

> e = MyException.new("foo", "bar", "baz")
> e.doSomething
> e.setWidget("widget")
> raise e
>

Hah! the raise operator (presumably a method in Kernel?) can take an
Object as its first parameter. Cool.

That wasn't mentioned in the Pragmatic Programmer's book (at least not
that I saw). Maybe I should have guessed that is how it worked..

Thanks

Simon

[Nikolai Weibull]

* Simon Kitching <simon@ecnetwork.co.nz> [Nov, 04 2003 10:40]:

> That wasn't mentioned in the Pragmatic Programmer's book ...

yes it is,
nikolai

--
::: name: Nikolai Weibull :: aliases: pcp / lone-star / aka :::
::: born: Chicago, IL USA :: loc atm: Gothenburg, Sweden :::
::: page: [url]www.pcppopper.org[/url] :: fun atm: gf,lps,ruby,lisp,war3 :::
main(){printf(&linux["\021%six\012\0"],(linux)["have"]+"fun"-97);}