On Tuesday, July 31, 2001, at 01:47 pm, Berin Loritsch wrote:
> Stuart Roebuck wrote:
>>
>> I'm trying to pin down a problem with components in Cocoon 2 at the
>> moment
>> and was trying to get to grips with Avalon. I ran across the following
>> code which didn't look like what I was expecting...
>>
>> "hasComponent()" which seems like a benign test, has the side-effect of
>> 'releasing' a component and appears to rely on "release()" not raising an
>> exception as the basis for determining the component's existence:
>
> It relies on the select() or lookup() function to not throw an exception.
> It
> could be rewritten to take advantage of the internal structure, but this
> approach
> is both future proof (it does not break if you reimplement the lookup() or
> select() functions) and correct. There is the possibility of trying to
> embed Objects that are not Components--which effectively removes the
> ability
> to get the Component.
By 'lookup()' do you mean 'release()'? There doesn't appear to be a
lookup() function/method.
But it still seems to me that if you call hasComponent() using the hint
for a component that has already been 'selected' then that component will
have been released by the time the hasComponent() method returns.
>>
>> ExcaliburComponentSelector.java:
>>> /**
>>> * Tests for existence of a component.
>>> */
>>> public boolean hasComponent( final Object hint )
>>> {
>>> if ( ! m_initialized ) return false;
>>> if ( m_disposed ) return false;
>>>
>>> boolean exists = false;
>>>
>>> try
>>> {
>>> this.release( this.select( hint ) );
>>> exists = true;
>>> }
>>> catch ( Throwable t )
>>> {
>>> // We can safely ignore all exceptions
>>> }
>>>
>>> return exists;
>>> }
>>
>> Apologies in advance if I'm being particularly stupid today! :-)
>>
>> Stuart.
-------------------------------------------------------------------------
Stuart Roebuck [EMAIL PROTECTED]
Lead Developer Java, XML, MacOS X, XP, etc.
ADOLOS <http://www.adolos.com/>
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