Oh, I wasn't suggesting a constructor that takes all the arguments,
I'm just wondering why this:
FetchOptions opts = FetchOptions.Builder.withLimit(10).offset(200);
...is better than this...
FetchOptions opts = new FetchOptions().limit(10).offset(200);
...or even...
FetchOptions opts = FetchOptions.create().limit(10).offset(200);
Adding the Builder with duplicate-but-differently-named methods seems awkward.
Jeff
On Thu, Apr 1, 2010 at 11:43 AM, Max Ross (Google)
<maxr+appeng...@google.com> wrote:
> Ok, we'll expose that method.
>
> With a public constructor it's very easy to mix up your args, especially
> when you have args of the same type. For example, someone is pretty much
> guaranteed to mix up the offset, limit, and prefetch args. A Builder
> prevents this. Josh Bloch has a nice chapter on this in the 2nd edition of
> Effective Java.
>
> Max
>
> On Thu, Apr 1, 2010 at 11:10 AM, Jeff Schnitzer <j...@infohazard.org> wrote:
>>
>> Yes, that would solve the problem. Although I have to wonder, how is
>> this any better than having a public constructor?
>>
>> Jeff
>>
>> On Thu, Apr 1, 2010 at 10:08 AM, Max Ross (Google)
>> <maxr+appeng...@google.com> wrote:
>> > Hi Jeff,
>> >
>> > Note that DatastoreServiceConfig exposes a withDefaults() method.
>> > FetchOptions has one too but it's package protected. We didn't expose
>> > it
>> > because FetchOptions isn't required for many low level datastore calls
>> > and
>> > we didn't see why users would want to create one if they didn't plan to
>> > adjust the offset, the limit, the prefetch size, etc. We didn't
>> > consider
>> > your use case though, and it makes perfect sense. Unless there's some
>> > other
>> > aspect of the Builder pattern that is getting in your way that you have
>> > explained, I think we could easily address your concern if we exposed
>> > FetchOptions.withDefaults(). Is that right?
>> >
>> > Thanks,
>> > Max
>> >
>> >
>> > On Thu, Apr 1, 2010 at 3:07 AM, Jeff Schnitzer <j...@infohazard.org>
>> > wrote:
>> >>
>> >> This is a genuine, heartfelt plea: The Builder pattern
>> >> (DatastoreServiceConfig, FetchOptions) makes code extra annoying when
>> >> layering an API on top of the low-level API.
>> >>
>> >> Let's say you are writing some code by hand that creates a
>> >> FetchOptions with a limit and an offset:
>> >>
>> >> FetchOptions opts = FetchOptions.Builder.withLimit(100).offset(20);
>> >>
>> >> Pretty straightforward when typing it out by hand, but the lack of
>> >> orthogonality between withLimit() and limit() is a PITA when you're
>> >> trying to automate the creation of a builder. The problem is, you
>> >> can't start with a "blank" FetchOptions. The result is we end up
>> >> writing lots of code like this:
>> >>
>> >> if (limit != null)
>> >> {
>> >> if (opts == null)
>> >> opts = FetchOptions.Builder.withLimit(limit);
>> >> else
>> >> opts = opts.limit(limit);
>> >> }
>> >>
>> >> This wouldn't be necessary if FetchOptions.Builder had a "create()"
>> >> method that would produce a blank FetchOptions. Or if FetchOptions
>> >> had a public constructor. Or if FetchOptions was an interface or even
>> >> a nonfinal class.
>> >>
>> >> I notice that DatastoreServiceConfig is following in the path of
>> >> FetchOptions. My initial reaction was Noooooo! :-)
>> >>
>> >> Thanks for listening,
>> >> Jeff
>> >>
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