Question

I am looking for a basic pattern where I can move some shared code. I have an NSManagedObject PurchaseOrder which is stored in Core Data. This can be edited and changed in several different views. Most of the time it is always the same type of change, PurchaseOrder is updated with data from another NSManagedObject Client.

I am wanting to move this type of code to a single place so I can call something like:

-(void) updatePurchaseOrder: (PurchasOrder *) aPurchaseOrder withClient:(Client *) aClient withManagedObjectContext: (NSManagedObjectContext *) aManagedObjectContext {
 // update code goes here
}

Is this a bad idea or a recipe for disaster? I do have a shared instance class I am using already (small bit of bit below):

static SharedFunctions* singletonInstance = nil;

-(id)init
{
    if ((self = [super init]))
    {

    }
    return self;
}


+(SharedFunctions*)sharedInstance
{
    @synchronized(self) {
        if (singletonInstance == nil) 
        {
            singletonInstance =  [[SharedFunctions alloc] init]; 
        }
    }
    return singletonInstance;
}

Which I call function like this:

[[[SharedFunctions] sharedInstance] myMethod];

This has been working well for me. Thoughts?

Answer 1

Where is your updatePurchaseOrder method defined? In this situation, I would create a custom PurchaseOrder subclass of the NSManagedObject and implement an updateWithClient method.

 @interface PurchaseOrder : NSManagedObject {
 }

-(void)updateWithClient:(Client *)client;

@end

So you can simply call [aPurchaseOrder updateWithClient:aClient]; where you need to. Seems more OO, unless I’m missing something?

If you’ve not made a custom subclass for PurchaseOrder, you could do the same thing in a category of NSManagedObject.