Re: NSDictionary.isEmpty
Re: NSDictionary.isEmpty
- Subject: Re: NSDictionary.isEmpty
- From: Chuck Hill <email@hidden>
- Date: Thu, 16 Sep 2010 10:06:25 -0700
On Sep 16, 2010, at 10:02 AM, Mark Ritchie wrote:
> Hey!
>
> On 16/Sep/2010, at 7:34 AM, ISHIMOTO Ken wrote:
>> Hi all, was a nice WOWODC, and really nice Job done Pascal.
> Glad to hear that WOWODC was fun... Too bad I missed it. OTOH, I head for Germany this weekend for my first european vacation so that's where my time off is going this year. ;-)
>
>> I have a small Problem about NSDictionary.
>> NSArray<Movie> movies= Movie.fetchAllMovies(defaultEditingContext());
>> EOEnterpriseObject eo = movies.objectAtIndex(0);
>> NSDictionary pDic = EOUtilities.primaryKeyForObject(defaultEditingContext(), eo);
>> System.err.println("1:" + pDic); -->1:{movieID = 102; }
>> System.err.println("isEmpty:" + pDic.isEmpty()); -->isEmpty:true
>> System.err.println("count:" + pDic.count()); -->count:1
>> Hadn't isEmpty not to be false ?
> I tried to reproduce your problem with a non-wonder app and could not. I was able to reproduce it with a Wonder app.
>
>> Also looking into isEmpty
>> public int count() {
>> return _count;
>> }
>> public boolean isEmpty() {
>> System.err.println("_count : " + _count); -->_count : 0
>> System.err.println("count() : " + count()); -->count : 1
>> return _count <= 0;
>> }
>> Why is the result of _count and count() different?
>> Any ideas what's going wrong?
> This was the part that really confused me until, I looked at this:
> System.err.println("pDic.getClass().getName() = " + pDic.getClass().getName());
> and I see:
> pDic.getClass().getName() = com.webobjects.eocontrol._EOMutableKnownKeyDictionary
>
> So, primaryKeyForObject() is returning a private subclass.
> And that subclass has it's own _count ivar.
> However it does not have an implementation of isEmpty() so it's inheriting the one from NSDictionary.
> Now, that's the WONDER version of NSDictionary. And it's using it's own _count ivar. :-(
Good one!
> The fix is to change NSDictionary.java's isEmpty() method to be:
> public boolean isEmpty() {
> return count() <= 0;
> }
>
> For the record, size() should be changed as well!
> And perhaps others, but I don't have unit tests for NSDictionary so I'm not changing anything! ;-)
Yet another reason to never use an ivar outside of the constructor or its accessor / mutator methods.
Chuck
--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their overall knowledge of WebObjects or who are trying to solve specific problems.
http://www.global-village.net/products/practical_webobjects
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