Anonymous user
Talk:Filter: Difference between revisions
how i made it worked (by the result point of view)
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Does it really works?! It does not on GNUstep, and looking at Apple's doc, I doubt it works for Mac OS X. NSPredicate does not cite the possibility of writing directly ''selectors-like string'' for NSExpression that way ([http://developer.apple.com/DOCUMENTATION/Cocoa/Conceptual/Predicates/Articles/pSyntax.html Cocoa predicates]); NSExpression has the expressionForFunction:arguments: where expressionForFunction can be @"modulus:by:" (and arguments is a NSArray) (see [http://developer.apple.com/DOCUMENTATION/Cocoa/Reference/Foundation/Classes/NSExpression_Class/Reference/NSExpression.html here]), but again, I've found no example about, nor citing, the fact that one can directly write a predicateWithFormat string expressing expressionForFunction ''directly'' with that syntax you've used, i.e. @"modulus:by:(SELF, 2)". Instead, I've tried a simpler @"intValue < 4" and it works like expected (the selector IntValue is for NSNumber object into the array...). GNUstep quirks or Cocoa facts? --[[User:ShinTakezou|ShinTakezou]] 18:16, 22 February 2009 (UTC)
The only way I get it working:
<lang objc>#import <Foundation/Foundation.h>
@interface NSNumber ( ExtFunc )
-(int) modulo2;
@end
@implementation NSNumber ( ExtFunc )
-(int) modulo2
{
return [self intValue] % 2;
}
@end
int main()
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSArray *numbers = [NSArray arrayWithObjects:[NSNumber numberWithInt:1],
[NSNumber numberWithInt:2],
[NSNumber numberWithInt:3],
[NSNumber numberWithInt:4],
[NSNumber numberWithInt:5], nil];
NSPredicate *isEven = [NSPredicate predicateWithFormat:@"modulo2 == 0"];
NSArray *evens = [numbers filteredArrayUsingPredicate:isEven];
NSLog(@"%@", evens);
[pool release];
return 0;
}</lang>
but maybe there's a way (a syntax) where I can extend NSNumber with a modulo:(int)num, which is more useful... (I've tried; then @"modulo: 2 == 0", @"(modulo: 2) == 0", @"modulo(2) == 0" all rise an error) --[[User:ShinTakezou|ShinTakezou]] 18:31, 22 February 2009 (UTC)
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