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iOS Swift 4：关闭或显示ViewController效率更高

[英]iOS Swift 4: ist it more efficient to dismiss or present a ViewController

原文 2018-12-03 09:08:53 3 2 ios/ swift/ view/ viewcontroller

In an iOS app, to move between screens, I can either present a new ViewController ("move forward") or dismiss a current ViewController ("move backward"). 在iOS应用中，要在屏幕之间移动，我可以显示一个新的ViewController（“向前移动”）或关闭当前的ViewController（“向后移动”）。

In my naive understanding, this is simply a way of moving back and forth in the stack of ViewControllers kept by the app. 以我幼稚的理解，这只是在应用程序保存的ViewController堆栈中来回移动的一种方式。

I have an intuitive preference for dismissing a ViewController (where possible) rather than presenting a new ViewController. 我有一个直观的偏好，就是解雇一个ViewController（如果可能的话），而不是展示一个新的ViewController。 It gives me the feeling of operating within a finite set of ViewControllers which in turn makes me feel the app is memory efficient. 它给我一种在有限的ViewControllers中操作的感觉，这反过来又让我感到该应用程序具有内存效率。

Say I am on View A and want to show View B, then presenting A would result in a stack ABA whereas dismissing B would keep the stack at A. 假设我在视图A上并想显示视图B，然后显示A将导致堆栈ABA，而关闭B将使堆栈保持在A。

My question is this: is that justified? 我的问题是：这合理吗？ is there any (programmatic) downside to perpetually working by presenting new ViewController? 提供新的ViewController是否有任何（编程的）缺点可以永久起作用？ Is it memory inefficient? 内存效率低下吗？

I wonder how many previous Views are being saved by the app and how long the stack could get, and if that is a reason to dismiss whenever possible. 我想知道应用程序正在保存多少个以前的视图，堆栈可以保存多长时间，这是否是一个尽可能取消的原因。

2 个解决方案

I am not 100% sure if i understood you correctly, but it seems in-efficient memory wise and not sure how possible it is. 我不确定我是否正确地理解了您，但不是100％肯定，但似乎内存使用效率低下，不确定该怎么做。 You want to keep going backward basically, just dismissing views, right? 您想基本上保持后退，只是取消视图，对吗？

Meaning when you load B, then A, then you want to dimiss A to go to B again? 意思是当您先加载B，然后加载A，然后又想放弃A再转到B？ Am i understanding this ok? 我可以理解吗？

In that case views would have to be in a constant "stack" and i am sure it will make things go slower, but more imporatantly, from user perspective and user experience, something that they are not used to at all :/ 在那种情况下，视图必须处于恒定的“堆栈”中，并且我确信它将使事情变慢，但更重要的是，从用户的角度和用户体验来看，它们是一点都不习惯的：/

My understanding would be: If you want to show A again, then you should be going back to the instance of screen A that you already have. 我的理解是：如果您想再次显示A，那么您应该回到已经拥有的屏幕A的实例。 There might be special cases where it makes sense to have multiple instances of A (like detail screens for different objects), but even then: What you definitely should not do is build a never-ending stack of view controllers because as you already assumed: This will consume lots of unnecessary memory. 在某些特殊情况下，拥有多个A实例是很有意义的（例如针对不同对象的详细信息屏幕），但是即使如此：您绝对不应该建立一个永无休止的视图控制器堆栈，因为您已经假设：这将消耗大量不必要的内存。

Maybe you should take a look at existing apps or the Apple Human Interface Guidelines and try to understand better how their view hierarchy works. 也许您应该看看现有的应用程序或《 Apple人机界面指南》，并尝试更好地了解它们的视图层次结构如何工作。