Ios error: Thread 1 under #auto release pool "EXC_BAD_ACCESS - ios

Question

The app crashes and shows this error when I hit the Back button. I have 2 view controllers. On the first vc the Start button works fine to switch to second view, but when I hit the Back button the app crashes and I get the error above on the line below #autorelease pool. I will also post the code for my start & back buttons. thx :)
#import
#import "AppDelegate.h"
int main(int argc, char *argv[])
{
#autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
}
}
First vc.H file Start Button (this works switching to second view)
#interface ViewController : UIViewController
{
IBOutlet UIButton *StartQuiz;
IBOutlet UIButton *HowToPlay;
IBOutlet UIButton *Credits;
IBOutlet UIButton *Back;
IBOutlet UILabel *Label;
}
-(IBAction)StartQuiz:(id)sender;
-(IBAction)HowToPlay:(id)sender;
-(IBAction)Credits:(id)sender;
-(IBAction)Back:(id)sender;
Firstvc.M file
#implementation ViewController
-(IBAction)StartQuiz:(id)sender {
Questions *MenuToQuestions = [[Questions alloc]
initWithNibName:#"Questions"
bundle:nil];
[self.view addSubview:MenuToQuestions.view];
}
SecondVC.h file (Back button crashes app)
#interface Questions : UIViewController
{
IBOutlet UIButton *BasicOptics;
IBOutlet UIButton *EyeAnatomy;
IBOutlet UIButton *OphthalmicInstruments;
IBOutlet UIButton *Lenses;
IBOutlet UIButton *Transposition;
IBOutlet UIButton *Standards;
IBOutlet UIButton *Frames;
IBOutlet UIButton *Random;
IBOutlet UIButton *Back;
IBOutlet UILabel *Cat1;
IBOutlet UILabel *Cat2;
IBOutlet UIButton *Right1;
IBOutlet UIButton *Right2;
IBOutlet UIButton *Right3;
IBOutlet UIButton *Right4;
IBOutlet UIButton *Wrong1;
IBOutlet UIButton *Wrong2;
IBOutlet UIButton *Wrong3;
IBOutlet UIButton *Wrong4;
IBOutlet UILabel *Answer1;
IBOutlet UILabel *Answer2;
IBOutlet UILabel *Answer3;
IBOutlet UILabel *Answer4;
IBOutlet UILabel *Question;
IBOutlet UILabel *SelectCategory;
IBOutlet UILabel *Lives;
IBOutlet UILabel *Score;
IBOutlet UILabel *LivesWord;
IBOutlet UILabel *ScoreWord;
IBOutlet UILabel *GameOver;
IBOutlet UILabel *FinalScore;
}
-(IBAction)BasicOptics:(id)sender;
-(IBAction)EyeAnatomy:(id)sender;
-(IBAction)OphthalmicInstruments:(id)sender;
-(IBAction)Lenses:(id)sender;
-(IBAction)Transposition:(id)sender;
-(IBAction)Standards:(id)sender;
-(IBAction)Frames:(id)sender;
-(IBAction)Random:(id)sender;
-(IBAction)Right:(id)sender;
-(IBAction)Wrong:(id)sender;
-(IBAction)Back:(id)sender;
#end
Secondvc.m file
-(IBAction)Back:(id)sender {
ViewController *MenuToViewController = [[ViewController alloc]
initWithNibName:#"ViewController"
bundle:nil];
[self.view addSubview:MenuToViewController.view];
}

Answer 1

You are not holding a reference for your MenuToViewController instance anywhere. The view of the MenuToViewController gets added to the view hierarchy, so it gets retained, but as soon as the view tries to send a message to one of the outlets, your app crashes, because the controller has been released.
Once you create that controller, you could set it as instance variable (add Questions *MenuToQuestions to your #interface).