IOS15全局设置返回按钮

全局类在UINavigationController进行
一种是上述方案，还有一种是继承一个BaseViewController，把父类的左边写好。其他类继承它，即可，这种不推荐。

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated{
    if(self.childViewControllers.count > 0){
        viewController.hidesBottomBarWhenPushed = YES;
        UIButton *backBtn = [[UIButton alloc] init];
         [backBtn setImage:[UIImage imageNamed:@"navigationButtonReturn"] forState:UIControlStateNormal];
         [backBtn setImage:[UIImage imageNamed:@"navigationButtonReturnClick"] forState:UIControlStateHighlighted];
         [backBtn setTitle:@"返回" forState:UIControlStateNormal];
         [backBtn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
         [backBtn setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
         [backBtn sizeToFit];
         backBtn.contentEdgeInsets = UIEdgeInsetsMake(0, -20, 0, 0);
         [backBtn addTarget:self action:@selector(baclClick) forControlEvents:UIControlEventTouchUpInside];
        viewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:backBtn];
        
    }
    
    [super pushViewController:viewController animated:animated];
    
}

-(void)baclClick{
    [self popViewControllerAnimated:YES];
}