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];
    }
}