IOS pop和present的区别

一、基本区别

pushViewController 导航控制器入栈的方式切换页面
presentViewController 模态切换的方式切换页面

二、对生命周期的影响

[self presentModalViewController:controller animated:YES];
self 不会调用dealloc自我销毁。
self.set 只会再第一次出现时调用ViewDidLoad加载，之后再执行该函数时只会调用：(void)viewWillAppear:(BOOL)animated;
[self dismissModalViewControllerAnimated:YES];
self 会调用dealloc
self之下的一个Controller会调用(void)viewWillAppear:(BOOL)animated;

[self.navigationController pushViewController:controller animated:YES];
上层的ViewController会调用viewdidload.
 [self.navigationController popViewControllerAnimated:YES];
上层的ViewController会调用dealloc

三、 A -> B -> C，在 C 中直接返回 A

3.1 用present实现的方法

C中返回事件 :

- (void)back  
{
    [self dismissModalViewControllerAnimated:NO]; // 注意一定是NO
    [[NSNotificationCenter  defaultCenter]postNotificationName:@"backback" object:nil];  
}

然后在B中 :

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(back) name:@"backback" object:nil];  
-(void)back  
{  
     [self dismissModalViewControllerAnimated:YES];  
}

3.2 pop的实现方法

返回到指定的控制器，要保证前面有入栈。

[self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:2] animated:YES];

也可以指定一个特定的控制器:

for (UIViewController *controller in self.navigationController.viewControllers) {
if ([controller isKindOfClass:[NeedBackViewController class]]) {
NeedBackViewController *vc = (NeedBackViewController *)controller;
[self.navigationController popToViewController:vc animated:YES];
}
}

四、判断当前是pop还是dismiss

4.1 通过判断self有没有present方式显示的父视图presentingViewController

- (IBAction)dismiss:(id)sender {
    if (self.presentingViewController) {
        [self dismissViewControllerAnimated:YES completion:nil];
    } else {
        [self.navigationController popViewControllerAnimated:YES];
    }
}

4.2 通过判断self.navigationController.viewControllers的最后一个是否是当前控制器，或者self.navigationController.topViewController == self

- (IBAction)dismiss:(id)sender {
    if (self.navigationController.topViewController == self) {
        [self.navigationController popViewControllerAnimated:YES];
    } else {
        [self dismissViewControllerAnimated:YES completion:nil];
    }
}