Re: Generics and Filtering on a Subclass
Re: Generics and Filtering on a Subclass
- Subject: Re: Generics and Filtering on a Subclass
- From: David Avendasora <email@hidden>
- Date: Mon, 23 Jun 2008 11:14:38 -0400
| Well, this works, but seems like I'm reinventing the wheel.
NSMutableArray<Finished> descendantFinisheds = new NSMutableArray<Finished>();
for (Part aPart : descendantParts()) {
if (aPart instanceof Finished) {
descendantFinisheds.addObject((Finished) aPart); }
}
And if I can force the casting of one object, why can't I force the casting of the Array using (NSArray<Finished>) EOQual...? On Jun 23, 2008, at 10:45 AM, David Avendasora wrote: Hi all,
I am trying to take an array (decendentParts()) of "Part" objects and filter only for the elements that are of the subclass "Finished".
Before Generics, I simply used: (yes, yes, I know I shouldn't be using qualifierWithQualifierFormat - please let it go, this one time)
EOQualifier qual = EOQualifier.qualifierWithQualifierFormat("partTypeId = 3", null);
NSArray descendantFinisheds = EOQualifier.filteredArrayWithQualifier(descendantParts(), qual);
But now, with generics, the compiler complains that it can't convert from "Part" to "Finished". Which I completely understand because there's no way for the compiler to know that I just filtered for a subclass and that all I'm going to get out of the filter process is Finished objects so the statement is valid. As far as it's concerned, I could be getting any subclass of "Part" back.
My question is, how do I filter so that the compiler will know that the results of the filter truly are Finished objects?
Dave
|
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