Encoding CGPoint struct with NSCoder

Question

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

Answer 1

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];

Answer 2

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

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

Answer 3

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];