I'm having difficulty keeping hold of property values from a copied object in objective-c

Question

I'm working with a model class and passing it back and forth between 3 controllers. I'm having trouble allowing customers to make selections on one controller and have them displayed in string form within a UILabel on another controller.

Each time the customer is taken to the controller where they make the selection and returned back to the previous controller, their selection is shown in string form as expected but previous selections are cleared. So I'm only able to show the selection for one category at a time.

Please read on for further details:

Controller 1 - The page that displays a collection view of clothing items

Controller 2 - A page the customer is taken to when tapping refine

Controller 3 - The page the customer selects the ways they wish to refine

In Controller 2 I display a list of different ways to refine search results by:

In Controller 3 the customer can make the actual selection:

I'm working with a class file which acts as my model. It's class is called VAGRefineModel. This class is first initialised in controller 1 and during the prepareForSegue method set as the value of a property of controller 2 called refineModel.

In controller 2 I pass a copy of the model to controller 3 using the prepareForSegue method again:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[[sender titleLabel] text] isEqualToString:@"Gender"]) {
        VAGRefineGenderViewController *vc = [segue destinationViewController];
        [vc setDelegate:self];
        [vc setRefineModel:[[self refineModel] copy]];
    }
}

Once customer lands on controller 3 they check what ever boxes are appropriate. Then by tapping the done button or tapping back the details are saved in the copy of the model. I use NSUserDefaults to track the status of my switches. This isn't important right now. The issue I'm having is after the customer returns to controller 2 their checkbox selection is displayed underneath the refine by option they chose. In my example you see underneath gender my selection is shown.

Ok this is fine but now when I tap on let's say brand to choose some more ways to refine my results then return back to controller 2 selection for gender is cleared and blank. I assume because the prepareForSegue method creates a new copy of my model to set as controller 3's refineModel property value.

I need a way to temporarily keep track of the selections made before the apply button is tapped. The apply button saves my copy model as the original models value. This is in place so that if a customer decides they don't wish to apply the selections they have made and return to controller 1 without tapping apply the original or previous selections if any, are returned.

More info:

I need a clear way to keep hold of all the data selected in controller 3. The way my app is set up it just gets reset.

Here is a delegate method from controller 3 that the model from controller 3 is passed to controller to in.

- (void)didTapDoneButtonWithRefineModel:(VAGRefineModel *)refineModel
{
    [self setRefineModel: refineModel];
}

I take the model passed over from controller 3 and set controller 2's property value to that. However this is the original I am setting. Nothing is saved unless apply button is tapped.

I have a UILabel under gender, brand, product type etc. This get's set upon returning to controller 2 from controller 3 depending on what's been selected.

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[self chosenGenders] setText:[[self refineModel] selectedGenderString]];
    [[self chosenBrands] setText:[[self refineModel] selectedBrandString]];
}

Question:

I need a way to keep those labels set once they have been set. If I return to controller 1 by tapping the back button everything is cleared. If apply button is tapped instead the data is stored in the original model.

How do I keep hold of the selection made in controller 3 no matter what?

Copy method as requested:

#import "VAGRefineModel.h"

@implementation VAGRefineModel
{
    VAGRefineModel *_object;
}

-(id)copyWithZone:(NSZone *)zone
{

    VAGRefineModel *modelCopy = [[VAGRefineModel alloc] init];
    modelCopy->_object = [_object copyWithZone: zone];
    return modelCopy;
}

Answer 1

As spotted by caleb the issue was with the copyWithZone method in my models implementation file. I wasn't setting the values of the copied models properties.

Editing the code show above to this solved my problem:

-(id)copyWithZone:(NSZone *)zone
{
    VAGRefineModel *modelCopy = [[VAGRefineModel allocWithZone: zone] init];

    [modelCopy setSelectedGenderString:[self selectedGenderString]];
    [modelCopy setSelectedBrandString:[self selectedBrandString]];
    // etc

    return modelCopy;
}

Also I've always avoided singletons as I believe as my app grows and becomes more complex they'll work against me. Using segue methods and delegates to pass data back and forth between controllers feels like I have more flexibility and also feels like the right thing to do.

Answer 2

As @Stonz2 proposed on the comment, you should make a singleton instance of the model, like an application model, to keep selections over the whole app and not passing a model instance between controllers.

Here's an example for a singleton implementation:

Singleton instance

There, add properties for

selectedGenderString 
selectedBrandString

and simply use this for setting:

[[VAGRefineModel sharedInstance] setSelectedGenderString:@"Some selected, other"];

and this for getting:

[[VAGRefineModel sharedInstance] selectedGenderString];

This is pure MVC philosophy! Hope it works for you.