Pass data to the parentViewController [iOS] - objective-c

Question

I have this storyboard:
When I press the "Insegnante" button in the first view controller (wich is called newCourseViewController) it show me a table view with a list of teacher. When I press on a teacher (and the method tableView:canEditRowAtIndexPath: is called) I want that the UITableViewController "pass" the object pressed to the first view controller.
This is my code for the first view controller newCourseViewController.h
#import <UIKit/UIKit.h>
#import "Teacher.h"
#interface newCourseViewController : UIViewController
#property (nonatomic , strong) Teacher *teacher;
#end
And this is my code for the first view controller newCourseViewController.m (only important code)
#import "newCourseViewController.h"
#import "Courses.h"
#import "Teacher.h"
#import "addTeacherToCourseViewController.h"
#interface newCourseViewController ()
#property (weak, nonatomic) IBOutlet UITextField *textField;
#end
#implementation newCourseViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(void)setTeacher:(Teacher *)teacher
{
self.teacher = teacher;
NSLog(#"Maestro settato!");
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"addTeacherToCourse"]) {
[segue.destinationViewController setPreviousViewController:self];
}
}
Now the code for the second view controller addTeacherToCourseViewController-h
#interface addTeacherToCourseViewController : UITableViewController
#property (nonatomic , weak) id previousViewController;
#end
and the addTeacherToCourseViewController.m (only the important method)
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
Teacher *teacher = [self.teachers getTeacherInPosition:indexPath.row];
[self.previousViewController setTeacher:teacher];
[self.navigationController popViewControllerAnimated:YES];
}
In the first view controller in the prepareForSegue method I set myself to the previousViewController in the second view. Then I "pass" the teacher selected and than I dismiss the second view controller.
When the application execute the [self.navigationController popViewControllerAnimated:YES]; Xcode crash and the simulator crash.
I can't figure out what is the problem. Can you help me?

Answer 1

To send values to parent controller you have to use protocols. I will provide proper steps you should take in order to have your desired functionality working.
1.
Create a protocol for your AddTeacherToCourseController.
In your AddTeacherToCourseController.h add the following right below the imports:
#protocol AddTeacherToCourseControllerProtocol <NSObject>
- (void)yourDelegateMethod:(Teacher *)insegnante;
#end
And below interface tag add:
#property (strong, nonatomic) id <AddTeacherToCourseControllerProtocol> delegate;
2.
In AddTeacherToCourseController.m:
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// I would use the existing array you are using to display the teachers in order to select the correct one you want to send back like this:
// Teacher *teacher = [self.teachers getTeacherInPosition:indexPath.row];
[self.delegate yourDelegateMethod:[yourTeacherArray objectAtIndex:indexPath.row]];
}
[this method will call your delegate method through the protocol and will pass your selected professor to the parent controller]
3.
In your parent controller, your newCourseViewController.h right after interface line add:
<AddTeacherToCourseControllerProtocol>
4.
If you do not have an Insegnante button action, create one in interface builder [dragging and naming]. Then add the following to this action:
// assuming your storyboard is named MainStoryboard. here you create your segue programmatically:
UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:#"MainStoryboard" bundle:nil];
addTeacherToCourseViewController *addTeacherController = (addTeacherToCourseViewController *)[storyBoard instantiateViewControllerWithIdentifier:#"addTeacherToCourseViewController"];
addTeacherController.delegate = self;
[self.navigationController pushViewController:addTeacherController animated:YES];
5.
In Interface Builder:
Remove your segue from Insegnante button.
Edit the Storyboard Id of 'addTeacherToCourseViewController' to 'addTeacherToCourseViewController'
6.
In newCourseViewController.h write your delegate method:
- (void)yourDelegateMethod:(Teacher *)insegnante{
// Do whatever you want with your Insegnante
// and be sure to pop the second controller from the view stack:
[self.navigationController popViewControllerAnimated:YES];
}
Let me know if you have questions and if my answer helped anyone.

Answer 2

In order to give you an exact answer please tell me what object you are using to display your list of professors in your second controller, the tableViewController. I am guessing that is an array of Teacher instances. Is that correct? [class Teacher]