From: Nit Khair <sentinel.2001@...>
Date: 2008-10-06T01:31:03+09:00
Subject: Re: "ensure" hiding actual error

Robert Klemme wrote:
> On 02.10.2008 14:48, Nit Khair wrote:
>>>> }
>>> This is common in Java, but it is incorrect.
>>>
>>> What happens if init_resource() throws an exception?
>> 
>> Oops I forgot to mention that in finally {} one would check for resource 
>> not being nil. Corrected above.
> 
> The pattern is still broken - or put it differently: overly complex.
> This is easier and as safe - and you can make the resource final and
> avoid accidental reassignment:
> 
> final Resource res = initResource();
> try {
>    res.use();
>    res.use();
>    res.use();
>    res.use();
> }
> finally {
>    res.cleanup();
> }
> 
> Cheers
> 
>   robert

Actually, I have left Java 4 years back. However, that being my last 
programming language i still tend to thing in that way. IIRC, the above 
pattern is used commonly because most, if not all, books gave it in 
their samples. Take file opening or a database connection, for example.

Since it can throw a file not found exception, or a database connection 
etc exception, the JDBC tutorials will recommend:

declare db variable
try {
   db = create_dbconnection(...)
   db.use

}
catch (ex){}
finally { cleanup code }


Anyway, I'd like to ask, if I use your suggested pattern of opening a 
file or creating a resource before a begin/rescue/ensure block, would 
that not mean i am not trapping failures from that. (I am just unused to 
thinking this way! Could you point me to some code that illustrates 
this.

Also, is there a quick way to know what exceptions a method can throw ? 
Or is that not relevant ?
-- 
Posted via http://www.ruby-forum.com/.