IOS How to make static alert

////////////////////////////////////////////////
CustomAlert.h
#import <Foundation/Foundation.h>

@interface CustomAlert : UIAlertView {
   
}

@property (nonatomic) BOOL isShow;

+ (CustomAlert*)sharedAlert;
- (void) createAlert:(NSString*) title message:(NSString*) message 
                               buttonTitle:(NSString*) btnTitle;
- (void) showAlert;
@end
//////////////////////////////////////////////// 
CustomAlert.m
////////////////////////////////////////////////
#import "CustomAlert.h"

@implementation CustomAlert
@synthesize isShow;
static CustomAlert *shared = NULL;
+ (CustomAlert*) sharedAlert {
    if (!shared || shared == NULL){
        // allocate the shared instance, because it hasn't been done yet
        shared = [[CustomAlert alloc] init];
        [shared addButtonWithTitle:@"OK"];
       
    }
    return shared;
}

- (void) createAlert:(NSString*) title message:(NSString*) message 
                               buttonTitle:(NSString*) btnTitle {
    if (!isShow) {
        self.message = message ;
        self.title = title;
        for (UIView *buttonView  in [self subviews]) {
            if ([buttonView isKindOfClass:[UIButton class]]) {
                UIButton *button = (UIButton*)buttonView;
                [button setTitle:btnTitle forState:UIControlStateNormal];
                break;
            }
        }
    }
}

- (void) showAlert {
    [self show];
    isShow = YES;
}

@end
Using static alert
CustomAlert *share1Alert = [CustomAlert sharedAlert];
  [share1Alert createAlert:@"Warning" message:@"Do you want to delete ?" buttonTitle:@"ok"] ;
  share1Alert.delegate = self;
  [share1Alert showAlert]; 

Hander click button on alert
- (void)alertView:(CustomAlert *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    alertView.isShow = NO;
 }