Encoding CGPoint struct with NSCoder

Question

How do you encode and decode a CGPoint struct using NSCoder?

Just leaving this here for others. In Swift on MacOSX CGPoint is the same as NSPoint: public func encodeWithCoder(coder: NSCoder) { coder.encodePoint(myNSPoint, forKey: "someKeyName") } — Jubei, Mar 09 '16 at 12:42

score 26 · Answer 1 · answered Jan 15 '09 at 23:23

26

To encode:

CGPoint point = /* point from somewhere */
NSValue *pointValue = [NSValue value:&point withObjCType:@encode(CGPoint)];
[coder encodeObject:pointValue forKey:@"point"];

To decode:

NSValue *decodedValue = [decoder decodeObjectForKey:@"point"];
CGPoint point;
[decodedValue getValue:&point];

answered Jan 15 '09 at 23:23

sbooth

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+1 This seems like a much better, less hackish general-purpose solution. – Quinn Taylor Mar 08 '10 at 22:50
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+1 BTW, you can use `(NSValue *)valueWithCGPoint:(CGPoint)point` class method. – Rudolf Adamkovič Aug 14 '13 at 18:27

score 17 · Answer 2 · edited Apr 16 '11 at 05:24

17

Just an update for iOS developers. You can do the following in Cocoa Touch (but not in Cocoa):

[coder encodeCGPoint:myPoint forKey:@"myPoint"];

edited Apr 16 '11 at 05:24

Cody Gray - on strike

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answered Apr 16 '11 at 01:31

Eric G

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And you can decode with [aDecoder decodeCGPointForKey:@"myPoint"]; – Chuck Krutsinger Jan 14 '14 at 21:53

score 10 · Accepted Answer · answered Jan 15 '09 at 19:51

10

CGPoints and NSPoints are both structures composed of two CGFloat values, so you can freely pass them around as each other. The quick and dirty way would be:

NSCoder *myNSCoder;
CGPoint myPoint;
[myNSCoder encodePoint:*(NSPoint *)myPoint];

This will usually work, but it technically breaks the C99 strict aliasing rules. If you want to be 100% compatible with the standard, you'll have to do something like:

typedef union
{
  CGPoint cgPoint;
  NSPoint nsPoint;
} CGNSPoint;

CGNSPoint cgnsPoint = { .cgPoint = myPoint };
[myNSCoder encodePoint:cgnsPoint.nsPoint];

answered Jan 15 '09 at 19:51

Adam Rosenfield

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However, if you’re building for the 64-bit runtime, or have NS_BUILD_32_LIKE_64 defined to 1, NSPoint and CGPoint are typedefed to the same struct, so no casting or union shenanigans are required. – Jens Ayton Jan 15 '09 at 20:55
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Furthermore, Foundation provides two inline functions named NSPoint{To,From}CGPoint. No need for pointer casting or a union. – Peter Hosey Jan 16 '09 at 02:30

Encoding CGPoint struct with NSCoder

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