IOS Delegation with custom class objects; pass object from modal view to parent view

Question

First, I apologize for asking another delegation question. I've read many and can't find any that deal with passing something complex...

Here's what I am doing... In my app, I have a ViewController: CollisionViewController where I want to let the user select two vehicles that are involved in a collision. All the vehicles are stored using CoreData and presented modally in SelectVehicleViewController. SelectVehicleViewController lists all the vehicles using a UICollectionView. In CollisionViewController, I have properties for Vehicle1 and Vehicle2 which are of a custom class that describes the properties of a vehicle.

In the CollisionViewController, I am using a UIButton to let the user first select Vehicle1, then Vehicle2 from SelectVehicleViewController presented modally.

I am using seques to determine which button was pressed before presenting the modal SelectVehicleViewController.

How do I setup a protocol that allows the user to pass the selected vehicle from the modal view to the correct vehicle object in the CollisionViewController?

Answer 1

collisionViewController should conform your protocol.

collisionViewController.h

#import "SelectVehicleViewController.h"
@interface ContactViewController : UIViewController <SelectVehicleDelegate>

collisionViewController.m

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqual:@"segueName"]) {
        SelectVehicleViewController* VC = segue.destinationViewController;
        VC.delegate = self;
        //here you should probably send if you will select the vehicule 1 or 2
    }
}

- (void)ViewController:(UIViewController *)sender
         didUpdateData:(NSString *)value {
    //do what you need with new data
    //here you should have info if it is for vehicle 1 or 2
}

SelectVehicleViewController.h

@protocol SelectVehicleDelegate;

@interface SelectVehicleViewController : UIViewController

@property (nonatomic, assign) id <SelectVehicleDelegate> delegate;

@end

@protocol SelectVehicleDelegate <NSObject>

- (void)ViewController:(UIViewController *)sender
             didUpdateData:(NSString *)value;      //adapte according to what you should send back

@end

SelectVehicleViewController.m

//somewhere in a button click or....
[self.delegate ViewController:self didUpdateData:@"new value"];
  //in this function you should have info if it is for vehicle 1 or 2