Cross-platform NSValue category

Question

I am trying to create a cross-platform NSValue category that will handle CGPoint/NSPoint and CGSize/NSSize etc, for Cocoa and iOS.

I have this:

#ifdef __MAC_OS_X_VERSION_MAX_ALLOWED
// Mac OSX

+ (NSValue *) storePoint:(NSPoint)point {
  return [NSValue valueWithPoint:point];
}

+ (NSPoint) getPoint {
  return (NSPoint)[self pointValue];
}


#else
// iOS

+ (NSValue *) storePoint:(CGPoint)point {
  return [NSValue valueWithCGPoint:point];
}

+ (CGPoint) getPoint {
  return (CGPoint)[self CGPointValue];
}


#endif

The Mac part works perfectly but the iOS part gives me an error on

  return (CGPoint)[self CGPointValue];

with two messages: 1) no known class method for selector CGPointValue and "used type CGPoint (aka struct CGPoint) where arithmetic or pointer type is required.

why is that?

there's no CGPointValue method on NSValue class. https://developer.apple.com/library/mac/documentation/cocoa/reference/foundation/classes/NSValue_Class/Reference/Reference.html — Andrey Chernukha, May 28 '14 at 11:46
@HutinPuylo There is in the [iOS rendition](https://developer.apple.com/library/ios/documentation/uikit/reference/NSValue_UIKit_Additions/Reference/Reference.html). — Rob, May 28 '14 at 11:49
@HutinPuylo it is here: https://developer.apple.com/library/ios/documentation/uikit/reference/NSValue_UIKit_Additions/Reference/Reference.html#//apple_ref/occ/instm/NSValue/CGPointValue — Bryan Chen, May 28 '14 at 11:50

score 2 · Accepted Answer · answered May 28 '14 at 11:48

2

because +[NSValue CGPointValue] does not exist you want -[NSValue CGPointValue]

#ifdef __MAC_OS_X_VERSION_MAX_ALLOWED
// Mac OSX

+ (NSValue *) storePoint:(NSPoint)point {
  return [NSValue valueWithPoint:point];
}

- (NSPoint) getPoint { // this should be instance method
  return (NSPoint)[self pointValue];
}


#else
// iOS

+ (NSValue *) storePoint:(CGPoint)point {
  return [NSValue valueWithCGPoint:point];
}

- (CGPoint) getPoint { // this should be instance method
  return (CGPoint)[self CGPointValue];
}


#endif

answered May 28 '14 at 11:48

Bryan Chen

45,816
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ahhh, ok, but out of curiosity, why Xcode is not giving me any error when I compile for Cocoa? – Duck May 28 '14 at 11:50
@RubberDuck I don't know... maybe somehow Xcode think `self` is `id` (untyped) so no type check was performed – Bryan Chen May 28 '14 at 11:51

score 1 · Answer 2 · answered Jan 08 '15 at 13:02

To make things even simpler, just create a category that is only for iOS and use the same method names as on OS X, since for OS X CGPoint & NSPoints are the same you don't need more, and you don't have to modify your OS X code.

@implementation NSValue (XCross)
#if TARGET_OS_IPHONE
+ (NSValue *) valueWithPoint:(CGPoint)point {
    return [NSValue valueWithCGPoint:point];
}

- (CGPoint) pointValue {
    return [self CGPointValue];
}
#endif
@end

score -2 · Answer 3 · answered May 28 '14 at 11:44

-2

+ (CGPoint) getPoint {
  return (CGPoint)[self CGPointValue];
}

Your variable begin by a maj ? isn't it better to set your variable with min. It may be a problem with CGPoint class.

[self cgPointValue];

answered May 28 '14 at 11:44

Plokstorm

27
1

No. This [is a Cocoa method](https://developer.apple.com/library/ios/documentation/uikit/reference/NSValue_UIKit_Additions/Reference/Reference.html). You cannot just change the name. The issue is that it's an instance method, not a class method. – Rob May 28 '14 at 11:51

Cross-platform NSValue category

3 Answers3