Core Data question

Question

Hi, the problem I am trying to solve in an application that is using Core Data is to be able to hold a calculated value in a NSManagedObject custom ivar. The calculated value that I want to store is in fact an image. I do not want to persist these images; I build them and destroy them throughout the lifetime of the application. I tried along the lines of:

@interface RTStaffImage : NSManagedObject {

UIImage *image;

}

// Custom properties
@property (nonatomic, retain) UIImage *image;
// Managed object properties
@property (nonatomic, retain) NSNumber *imageID;
@property (nonatomic, retain) NSString *imageName;

and custom accessors methods:

- (void)setImage (UIImage*)im;
- (UIImage *)image;

and in the implementation:

@implementation RTStaffImage

@synthesize image;
@dynamic imageID;
@dynamic imageName;

This fails at runtime with unrecognised selector problems:

-[NSManagedObject setImage:]: unrecognized selector sent to instance

The above approach is what Apple (or, at least as far as I see having read the docs) outlines for transient properties so it should work :-(

Any ideas, comments?

Answer 1

Yeah, you have these backwards:

@synthesize image;
@dynamic imageID;
@dynamic imageName;

You're providing an implementation for setImage and image, so image should be @dynamic, and the others you need synthesized methods for, so use @synthesize for imageID and imageName.

Good point, they should all be @dynamic since you're with CoreData.

2nd attempt: you have set RTStaffImage as the Class name in the Entity, right?

3rd attempt: is RTStaffImage.m actually part of the Target being built?

Answer 2

- (void)setImage (UIImage*)im;

you are missing a colon between setImage and (UIImage*). This is the correct version:

- (void)setImage:(UIImage*)im;

And where are the implementations of those two methods?

---

-[NSManagedObject setImage:]: unrecognized selector sent to instance

just curious, I read NSManagedObject there, are you sure you create an instance of RTStaffImage there?