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]

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.

 

[Joel VanderWerf]

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]

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]

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]

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

yes it is,
nikolai