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From Matt Benson <gudnabr...@gmail.com>
Subject Re: [CSV] Prohibit creation of more than one iterator over a CSVParser?
Date Tue, 13 Aug 2013 14:00:46 GMT
One approach I think I've actually used at some point is for the same class
to implement both Iterator and Iterable, implementing #iterator() as
`return this`.  While it seems a little weird, it's really just a more
explicit reflection of what the current code is doing and so, at least in
this case, it seems to me justifiable.  WDYT?

Matt


On Tue, Aug 13, 2013 at 8:39 AM, Benedikt Ritter <britter@apache.org> wrote:

> We had that before but switched to Iterable to make it possible to use
> CSVPaarser in foreach loops.
>
>
> 2013/8/13 Matt Benson <gudnabrsam@gmail.com>
>
> > My thinking was more that CSVParser itself implements Iterator.
> >
> > Matt
> > On Aug 13, 2013 2:59 AM, "Benedikt Ritter" <britter@apache.org> wrote:
> >
> > > Hi Matt,
> > >
> > >
> > > 2013/8/12 Matt Benson <gudnabrsam@gmail.com>
> > >
> > > > As someone with no prior involvement with this component, and at risk
> > of
> > > > being hit by the digital tomatoes of the group, this seems to
> indicate
> > to
> > > > me that once a parser definition has been joined to a source of
> input,
> > > the
> > > > resulting object *is* the record iterator.  If there's no way to
> twist
> > > that
> > > > into a comfortable API, I would tend to agree with Benedikt:  calling
> > > > #iterator() a second time should do something like triggering an
> > > > IllegalStateException().
> > > >
> > >
> > > No tomatoes, don't worry ;-) feedback is always welcome.
> > >
> > > I'm not sure I understand what you're suggesting. Are you thinking of
> > > something like:
> > >
> > > Iterator<CSVRecord> itr = CSVParser.parse(myCsvFile);
> > >
> > > CSVParser has some features that go beyond the capabilities of the
> > > Iterator() interface. For example one can ask the parser for the
> current
> > > line number in your input and the current record number (which may not
> be
> > > the same for multi line records).
> > > How about extending the Iterator interface?
> > >
> > > CSVIterator itr = CSVParser.parse(myCsvFile);
> > >
> > > and CSVIterator would look like:
> > >
> > > public interface CSVIterator extends Iterator<CSVRecord> {
> > >    // call the cool CSVParser stuff goes here
> > > }
> > >
> > > But this wouldn't prevent more than one iterator over the same
> source...
> > >
> > > Benedikt
> > >
> > >
> > > >
> > > > $0.02,
> > > > Matt
> > > >
> > > >
> > > > On Mon, Aug 12, 2013 at 4:43 PM, Gary Gregory <
> garydgregory@gmail.com
> > > > >wrote:
> > > >
> > > > > On Mon, Aug 12, 2013 at 3:26 PM, Benedikt Ritter <
> britter@apache.org
> > >
> > > > > wrote:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > I've added a new test to CSVParser test case that shows what
> > happens
> > > if
> > > > > > CSVParser.iterator() is called twice [1].
> > > > > >
> > > > > > This looks pretty strange to me. One iterator can eat up records
> of
> > > the
> > > > > > other.
> > > > > > Would it be better to throw an exception if iterator() is called
> > more
> > > > > than
> > > > > > once?
> > > > > >
> > > > >
> > > > > Yeah, there is something odd about the current impl. Wouldn't it
be
> > > > obvious
> > > > > what can be done if there is an iterator ivar and the accessor just
> > > > returns
> > > > > it? It does not even have to be lazy initialized.
> > > > >
> > > > > Gary
> > > > >
> > > > >
> > > > > >
> > > > > > Benedikt
> > > > > >
> > > > > > [1] http://svn.apache.org/r1513228
> > > > > >
> > > > > >
> > > > > > --
> > > > > > http://people.apache.org/~britter/
> > > > > > http://www.systemoutprintln.de/
> > > > > > http://twitter.com/BenediktRitter
> > > > > > http://github.com/britter
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > E-Mail: garydgregory@gmail.com | ggregory@apache.org
> > > > > Java Persistence with Hibernate, Second Edition<
> > > > > http://www.manning.com/bauer3/>
> > > > > JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
> > > > > Spring Batch in Action <http://www.manning.com/templier/>
> > > > > Blog: http://garygregory.wordpress.com
> > > > > Home: http://garygregory.com/
> > > > > Tweet! http://twitter.com/GaryGregory
> > > > >
> > > >
> > >
> > >
> > >
> > > --
> > > http://people.apache.org/~britter/
> > > http://www.systemoutprintln.de/
> > > http://twitter.com/BenediktRitter
> > > http://github.com/britter
> > >
> >
>
>
>
> --
> http://people.apache.org/~britter/
> http://www.systemoutprintln.de/
> http://twitter.com/BenediktRitter
> http://github.com/britter
>

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