Core Data transient attributes - how to add needed custom code to category to preserve autogeneration of managed object sub class files

Category+Transient.h

#import "Category.h"

@interface Category (Transient)

@property (nonatomic, strong) UIColor *color;

- (UIColor *)primitiveColor;
- (void)setPrimitiveColor:(UIColor *)value;
- (NSData *)primitiveColorData;
- (void)setPrimitiveColorData:(NSData *)value;
@end

Category+Transient.m

#import "Category+Transient.h"

// this implementation will trigger a warning that it is incomplete, lacking definitions for primitiveColor
// setPrimitiveColor, primitiveColorData, setPrimitiveColorData

@implementation Category (Create)
@dynamic color;


- (UIColor *)color
{
    [self willAccessValueForKey:@"color"];
    UIColor *tempColor = [self primitiveColor];
    [self didAccessValueForKey:@"color"];
    
    if (tempColor) {
        return tempColor;
    }
    
    NSData *tempColorData = [self colorData];
    if (!tempColorData) {
        return nil;
    }
    tempColor = [NSKeyedUnarchiver unarchiveObjectWithData:tempColorData];
    [self setPrimitiveColor:tempColor];
    
    return tempColor;
    
}

- (void)setColor:(UIColor *)aColor {
    
    [self willChangeValueForKey:@"color"];
    [self setPrimitiveValue:aColor forKey:@"color"];
    [self didChangeValueForKey:@"color"];
    [self setValue:[NSKeyedArchiver archivedDataWithRootObject:aColor]
            forKey:@"colorData"];
}

- (void)willSave
{
    UIColor *tempColor = [self primitiveColor];
    
    if ( tempColor ) {
        [self setPrimitiveColorData:[NSKeyedArchiver archivedDataWithRootObject:tempColor]];
    }
    else {
        [self setPrimitiveColor:nil];
    }
    
    [super willSave];
}


@end

category.h

// autogenerated 


#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

@class SubReceipt;

@interface Category : NSManagedObject

@property (nonatomic, strong) NSString * name;
@property (nonatomic, strong) NSData * colorData;
//@property (nonatomic, strong) UIColor *color;



@end

category.m

// autogenerated

#import "Category.h"
#import "SubReceipt.h"


@implementation Category

@dynamic name;
@dynamic colorData;
//@dynamic color;


@end

CategoryTransient.h

#import "Category.h"

@interface Category (Transient)

@property (nonatomic, strong) UIColor *color;
@property (nonatomic, strong) UIColor *primitiveColor;
@property (nonatomic, strong) NSData *primitiveColorData;
/* when used in a category, this will lead to incomplete implementation warnings
- (UIColor *)primitiveColor;
- (void)setPrimitiveColor:(UIColor *)value;
- (NSData *)primitiveColorData;
- (void)setPrimitiveColorData:(NSData *)value;
*/
@end

CategoryTransient.m

#import "Category+Transient.h"

// this implementation will trigger a warning that it is incomplete, lacking definitions for primitiveColor
// setPrimitiveColor, primitiveColorData, setPrimitiveColorData

@implementation Category (Create)
@dynamic color;
@dynamic primitiveColor;
@dynamic primitiveColorData;


- (UIColor *)color
{
    [self willAccessValueForKey:@"color"];
    UIColor *tempColor = [self primitiveColor];
    [self didAccessValueForKey:@"color"];
    
    if (tempColor) {
        return tempColor;
    }
    
    NSData *tempColorData = [self colorData];
    if (!tempColorData) {
        return nil;
    }
    tempColor = [NSKeyedUnarchiver unarchiveObjectWithData:tempColorData];
    [self setPrimitiveColor:tempColor];
    
    return tempColor;
    
}

- (void)setColor:(UIColor *)aColor {
    
    [self willChangeValueForKey:@"color"];
    [self setPrimitiveValue:aColor forKey:@"color"];
    [self didChangeValueForKey:@"color"];
    [self setValue:[NSKeyedArchiver archivedDataWithRootObject:aColor]
            forKey:@"colorData"];
}

- (void)willSave
{
    UIColor *tempColor = [self primitiveColor];
    
    if ( tempColor ) {
        [self setPrimitiveColorData:[NSKeyedArchiver archivedDataWithRootObject:tempColor]];
    }
    else {
        [self setPrimitiveColor:nil];
    }
    
    [super willSave];
}


@end