Indexing Core Data Managed Objects

- (NSMutableArray *) orderedComponents{
        NSSortDescriptor *orderSort=[[NSSortDescriptor alloc] initWithKey:[ComponentToLabelMO order_Key]
                                                                                                                        ascending:YES];
        //------------------------------------------------------^
        NSArray *sorted=[[[self components] allObjects] sortedArrayUsingDescriptors:[NSArray arrayWithObject:orderSort]];
        self.orderedComponents=[[NSMutableArray alloc] initWithArray:sorted]; //use self.property= to handle retention
        return orderedComponents;
}

- (ComponentToLabelMO *) componentAtIndex:(NSUInteger) index{
        return [self.orderedComponents objectAtIndex:index];
}

// I use the NSMutableArray methods to manage the order for me.
-(void) updateComponentOrder{
        NSUInteger i, count = [self.orderedComponents count];
        for (i = 0; i < count; i++) {
                ComponentToLabelMO* component = [self.orderedComponents objectAtIndex:i];
                component.order=[NSNumber numberWithUnsignedInt:i];
        }
}

// creates new linking object and assigns it's order to the end of the label
- (void) addComponentToLabelWithComponent:(LabelComponentMO *) aLabelComponent{
        ComponentToLabelMO *ctlMO=[NSEntityDescription insertNewObjectForEntityForName:[ComponentToLabelMO entityName]
                                                                                                                  inManagedObjectContext:self.managedObjectContext];
                //------------------------------------------------^
        ctlMO.label=self; //this will add the ctl automatically to self.components
        ctlMO.component=aLabelComponent;
        ctlMO.order=[NSNumber numberWithInt:[self.orderedComponents count]]; //the order is zero indexed so first labels order is zero, second is one etc

}

//Used to add a component to the end of the index i.e. when order is not known or needed
- (void) addComponent:(LabelComponentMO *) aLabelComponent;{
        if (aLabelComponent!=nil) {
                [self addComponentToLabelWithComponent:aLabelComponent]; //automatically add at end of order
                [self updateComponentOrder];
        }
}

// Used to add a component to a specific index in the lable
- (void) addComponent:(LabelComponentMO *) aLabelComponent AtIndex:(NSUInteger) index{
        if (aLabelComponent!=nil) {
                [self addComponentToLabelWithComponent:aLabelComponent];
                [self.orderedComponents exchangeObjectAtIndex:[self.orderedComponents count] withObjectAtIndex:index];
                [self updateComponentOrder];
        }
}


- (void) swapComponentAtIndex:(NSUInteger) firstIndex withComponentAtIndex:(NSUInteger) otherIndex{
        NSUInteger comCount=[self.orderedComponents count];
        if ( (firstIndex<=comCount) && (otherIndex<=comCount) ){ // prevent range exception
                [self.orderedComponents exchangeObjectAtIndex:firstIndex withObjectAtIndex:otherIndex];
                [self updateComponentOrder];
        }

}

- (void) removeComponentAtIndex:(NSUInteger) index{
        if (index<=[self.orderedComponents count]) {
                ComponentToLabelMO *removedLabel=[self.orderedComponents objectAtIndex:index];
                [self removeComponentsObject:removedLabel];
                [self updateComponentOrder];
        }
}