viewcontroller present AlertController 点击cancel后调用了viewcontroller重写的dismiss

[kane313]

viewControllerA present ViewControllerB 在B中点击按钮present alertController 点击cancel按钮后调用了B中重写的- (void)dismissViewControllerAnimated: (BOOL)flag completion: (void (^ __nullable)(void))completion 请问这是为什么？

#import "testViewController.h"

@interface testViewController ()

@end

@implementation testViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button setTitle:@"button" forState:UIControlStateNormal];
    [button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    button.frame = self.view.bounds;
    // Do any additional setup after loading the view.
}
- (void)dismissViewControllerAnimated:(BOOL)flag completion:(void (^)(void))completion{
//这里在点击alertController上的cancel按钮会被执行
    [super dismissViewControllerAnimated:flag completion:completion];
}
- (void)buttonAction{
    UIAlertController* alertController = [UIAlertController alertControllerWithTitle:@"awdad" message:@"dawwaea" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction* action = [UIAlertAction actionWithTitle:@"cancel" style:UIAlertActionStyleCancel handler:nil];
    [alertController addAction:action];
    [self presentViewController:alertController animated:YES completion:nil];
}