UIAlertController Warning Message - ios8

Question

I am using the below code for UIAlertController in my project.
if([[[UIDevice currentDevice] systemVersion]floatValue] >= 8.0){
UIAlertController * alert= [UIAlertController
alertControllerWithTitle:#"Input Error"
message:#"Please enter a valid email."
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* okAction = [UIAlertAction
actionWithTitle:#"OK"
style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action)
{
[alert dismissViewControllerAnimated:YES completion:nil];
}];
[alert addAction:okAction];
[self presentViewController:alert animated:YES completion:nil];
}
else
{
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"Input Error"
message:#"Please enter a valid email"
delegate:self
cancelButtonTitle:#"OK"
otherButtonTitles:nil, nil];
[alertView show];
}
I am getting the below waring message:
Warning: Attempt to present <UIAlertController: 0x7f8da58df1f0> on <MBComplaintsViewController: 0x7f8da36454d0> which is already presenting (null)
Kindly guide me how to properly use UIAlertController using Objective C.
Thanks,
Abin Koshy Cheriyan

Answer 1

Yes as per #Alexander you should not be dismissing the alert controller like this explicitly.
As per an apple engineer a new window gets added each time an UIAlertController is displayed so when we go for dismissing it the window is still there though the alert controller disappears.
So there are two ways to handle this -
Way 1 - No explicit dismiss
Do not explicitly dismiss the UIAlertController, let it be done by the user
Way 2 - Use your own window
Simply create a category on UIAertController
Here is the sample code -
.h
#import <UIKit/UIKit.h>
#interface UIAlertController (MyAdditions)
#property(nonatomic,strong) UIWindow *alertWindow;
-(void)show;
#end
In .m
#import "UIAlertController+MyAdditions.h"
#import <objc/runtime.h>
#implementation UIAlertController (MyAdditions)
#dynamic alertWindow;
- (void)setAlertWindow:(UIWindow *)alertWindow {
objc_setAssociatedObject(self, #selector(alertWindow), alertWindow, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (UIWindow *)alertWindow {
return objc_getAssociatedObject(self, #selector(alertWindow));
}
- (void)show {
self.alertWindow = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.alertWindow.rootViewController = [[UIViewController alloc] init];
// window level = topmost + 1
UIWindow *topWindow = [UIApplication sharedApplication].windows.lastObject;
self.alertWindow.windowLevel = topWindow.windowLevel + 1;
[self.alertWindow makeKeyAndVisible];
[self.alertWindow.rootViewController presentViewController:self animated:YES completion:nil];
}
-(void)hide {
self.alertWindow.hidden = YES;
self.alertWindow = nil;
}
- (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
// just to ensure the window gets desroyed
self.alertWindow.hidden = YES;
self.alertWindow = nil;
}
To show the alert controller
UIAlertCntroller *alert = ## initialisation##;
// will show the alert
[alert show];
//to dismiss
[alert hide];
[alert dismissViewControllerAnimated:YES completion:nil];
Even you can checkout one of my sample implementation here

Answer 2

I don't know about your problem, but you shouldn't do that
handler:^(UIAlertAction * action)
{
[alert dismissViewControllerAnimated:YES completion:nil];
}];
It will be anyway dismissed on any of your actions.