Encoding c-struct with Mantle (NSCoding) - ios

Question

I want to use Mantle framework (https://github.com/github/Mantle) to support NSCoding for my class with struct property:
typedef struct {
int x;
int y;
} MPoint;
typedef struct {
MPoint min;
MPoint max;
} MRect;
#interface MObject : MTLModel
#property (assign, nonatomic) MRect rect;
#end
#implementation MObject
#end
But when I tried to [NSKeyedArchiver archiveRootObject:obj toFile:#"file"]; its crashed in MTLModel+NSCoding.m, in - (void)encodeWithCoder:(NSCoder *)coder on line
case MTLModelEncodingBehaviorUnconditional:
[coder encodeObject:value forKey:key];
Does Mantle supports c-struct encoding (and also decoding) or I've need to custom implementing NSCoding protocol for such classes?

Answer 1

My original data structure is an XML (yeah, I know):
...
<Lat>32.062883</Lat>
<Lot>34.782904</Lot>
...
I used MTLXMLAdapter based on KissXML, but you can see how it's applicable to any other serializer.
+ (NSValueTransformer *)coordinateXMLTransformer {
return [MTLValueTransformer reversibleTransformerWithBlock:^id(NSArray *nodes) {
CLLocationCoordinate2D coordinate;
for (DDXMLNode *node in nodes) {
if ([[node name] isEqualToString:#"Lat"]) {
coordinate.latitude = [[node stringValue] doubleValue];
} else if ([[node name] isEqualToString:#"Lot"]) {
coordinate.longitude = [[node stringValue] doubleValue];
}
}
return [NSValue value:&coordinate
withObjCType:#encode(CLLocationCoordinate2D)];
}];
}
You can add a reverseBlock if needed.

Answer 2

It was easier than I thought:
Exclude property in +encodingBehaviorsByPropertyKey
Manual encode/encode excluded property
Sample:
#pragma mark - MTLModel + NSCoding
- (id)initWithCoder:(NSCoder *)coder {
self = [super initWithCoder:coder];
if (self) {
self.rect = [[self class] mRectFromData:[coder decodeObjectForKey:#"rectData"]];
}
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[super encodeWithCoder:coder];
[coder encodeObject:[[self class] dataFromMRect:self.rect] forKey:#"rectData"];
}
+ (NSDictionary *)encodingBehaviorsByPropertyKey {
NSDictionary *excludeProperties = #{
NSStringFromSelector(#selector(rect)): #(MTLModelEncodingBehaviorExcluded)
};
NSDictionary *encodingBehaviors = [[super encodingBehaviorsByPropertyKey] mtl_dictionaryByAddingEntriesFromDictionary:excludeProperties];
return encodingBehaviors;
}
#pragma mark - MRect transformations
+ (MRect)mRectFromData:(NSData *)rectData {
MRect rect;
[rectData getBytes:&rect length:sizeof(rect)];
return rect;
}
+ (NSData *)dataFromMRect:(MRect)rect {
return [NSData dataWithBytes:&rect length:sizeof(rect)];
}