If you wish to handle FooError and UnrelatedToFooError in the same way, you can use the concatenation operator:
 
     [ someObject foo ]
         on: FooError, UnrelatedToFooError
         do: [ : err | "handle the err" ]
 
 If, however, you wish to handle them differently you may nest them:
 
     [ [ someObject foo ]
         on: FooError
         do: [ :fooErr | "handle fooErr" ] ]
             on: UnrelatedToFooError
             do: [ :unToFooErr | "..." ]
 
 For this second case, I implemented a helper method on BlockContext that allows me to specify multiple handlers conveniently without nesting:
 
 BlockContext>>#maOn: exc1 do: block1 on: exc2 do: block2
     ^ [
             [ self value ]
                 on: exc1
                 do: block1 ]
 
         on: exc2
         do: block2
 
 Hope this helps..
 
  - Chris

 
----- Original Message ----
From: Zulq Alam <zulq at orange.net>
To: The general-purpose Squeak developers list <squeak-dev at lists.squeakfoundation.org>
Sent: Monday, March 20, 2006 2:12:48 PM
Subject: Exception Handling

Hello,

I'm a bit confused about exception handling, perhaps you can help please?

If I have a method #foo and #foo can signal two errors FooError and
UnrelatedToFooError how do I handle both errors using #on:do: without
having something like...

[someObject foo]
    on: Error
    do: [:error | (error class = FooError) ifTrue: ["do something
specific to FooError"].
          (error class = UnrelatedToFooError) ifTrue: ["do something
specific to UnrelatedToFooError"]].

In Java I would do something like

try {
    somObject.foo();
}
catch (FooError e) {
    // do something specific to FooError
}
catch (UnrelatedToFooError e) {
    // do something specific to UnrelatedToFooError
}

Even if under the hood the same is happening this seems to take care of
some very common code.

Is there something in Smalltalk/Squeak will provide something similar?

Thanks,
Zulq.