How to refer previous view controller?

Question

I have three view controllers(VC). My second VC has a start button and third VC I set a label top right corner for a time.If I click the start button(in second VC) then the time should run when I move to the third VC. How to do this? For a quiz app.

Answer 1

You can do this easily:

Use storyboard create UI:

The code is below:

ViewController2.m:

#import "ViewController2.h"

@interface ViewController2 ()
{
    NSTimer *timer;
    int time_count;
}
@property (weak, nonatomic) IBOutlet UILabel *time_label;

@end

@implementation ViewController2

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.


    timer = [NSTimer scheduledTimerWithTimeInterval:1
                                             target:self
                                           selector:@selector(handleTimer:)
                                           userInfo:nil
                                            repeats:YES];

}
/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

- (void)handleTimer:(id )sender {

    _time_label.text = [NSString stringWithFormat:@"%d", time_count++];

}

@end

The result is like this:

---

Swift 3

The main code:

import UIKit

class ViewController2: UIViewController {

    @IBOutlet weak var time_label: UILabel!

    var time_count = 0

    override func viewDidLoad() {
        super.viewDidLoad()


        Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(timerHandler), userInfo: nil, repeats: true)

    }

    func timerHandler() {

        self.time_count += 1
        self.time_label.text = "\(self.time_count)"
    }

}