How to turn off Torch when leaving (segue) from view? - ios

Question

I have made an app that utilizes Torch. I have a button that turns torch on / off. However, if user turns torch on, then navigates away from view, torch stays on. User must navigate back to view to turn off. What I want is for the torch to turn off automatically when user navigates away from page.
Using Xcode 5.1.1; ios 7; this app primarily for iPhone
Here is the code I use for Torch:
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize btnFlash;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)btnFlashOnClicked:(id)sender
{
AVCaptureDevice *flashLight = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if ([flashLight isTorchAvailable] && [flashLight isTorchModeSupported:AVCaptureTorchModeOn])
{
BOOL success = [flashLight lockForConfiguration:nil];
if (success)
{
if ([flashLight isTorchActive])
{
[btnFlash setTitle:#"Light On" forState:UIControlStateNormal];
[flashLight setTorchMode:AVCaptureTorchModeOff];
}
else
{
[btnFlash setTitle:#"Light Off" forState:UIControlStateNormal];
[flashLight setTorchMode:AVCaptureTorchModeOn];
}
[flashLight unlockForConfiguration];
}
}
}
#end

Answer 1

OK, break down the functionality into methods that allow easy querying of the current light state and methods to turn it on or off:
- (AVCaptureDevice *)flashLight
{
AVCaptureDevice *flashLight = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if (![flashLight isTorchAvailable] ||
![flashLight isTorchModeSupported:AVCaptureTorchModeOn]) {
flashLight = nil;
}
return flashLight;
}
- (BOOL)isLightOn
{
BOOL isOn = NO;
AVCaptureDevice *flashLight = [self flashLight];
if ([flashLight lockForConfiguration:nil]) {
isOn = [flashLight isTorchActive];
[flashLight unlockForConfiguration];
}
return isOn;
}
- (void)turnLightOn:(BOOL)on
{
AVCaptureDevice *flashLight = [self flashLight];
if ([flashLight lockForConfiguration:nil]) {
[flashLight setTorchMode:on ? AVCaptureTorchModeOn : AVCaptureTorchModeOff];
[flashLight unlockForConfiguration];
}
}
as that will make it easier to simply call turnLightOn:NO regardless of the current state and easier to manipulate in your action method:
- (IBAction)btnFlashOnClicked:(id)sender
{
BOOL newState = ![self isTorchOn];
[self turnLightOn:newState];
[btnFlash setTitle:newState ? #"Light Off" : #"Light On"
forState:UIControlStateNormal];
}
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[self turnLightOn:NO];
}

Answer 2

You could turn the torch off inside the method:
- (void)viewDidDisappear:(BOOL)animated
simply paste the following in your view controller:
- (void)viewDidDisappear:(BOOL)animated{
[super viewDidAppear:animated];
// your code to turn the torch off goes here
}