子类化 UIView 与 UIScrollView [英] Subclassing UIView vs UIScrollView

问题描述

好吧，这可能是不可能的，但我有一个类(称为 CompositeView)，它是 UIView 的子类.它使用一些核心图形工作根据某些选项生成自定义背景.不是一个庞大的班级，但随着我的需求变化/增加/无论什么都会增长.我遇到的问题是我在很多不同的地方经常使用这个类.但在一些地方，我需要它是 UIScrollView 的子类，而不是 UIView.有趣的是，我可以简单地更改超类，并且一切正常.但我不仅不希望我的所有其他视图都成为 UIScrollView，它还会干扰其中一些视图的操作.所以我需要一个类，它有时是 UIScrollView 的子类，有时是 UIView 的子类.

Ok, this might not be possible, but I've got a class (called CompositeView) that's a subclasses UIView. It uses some core graphics work to produce a custom background based on some options. Not a huge class, but bound to grow as my demands change/increase/whatever. The problem I'm having is I use this class a lot, in a lot of different places. But in a few of the places I need it to be a subclass of UIScrollView instead of a UIView. Interestingly enough, I can simply change the superclass and it all works perfectly fine. But not only do I not want all my other views to be a UIScrollView, it also interferes with the operation of some of them. So I need a class that's sometimes a subclass of UIScrollView and sometimes a subclass of UIView.

现在，我从字面上复制了 CompositeView 的所有接口/实现，将类名更改为 CompositeScrollView，并将其继承更改为 UIScrollView.它工作正常，但现在我有两组代码做完全相同的事情，只是从不同的父类继承.这使得让他们都保持最新状态很痛苦.

For now, I've literally copied all of the interface/implementation of the CompositeView, changed the class name to CompositeScrollView, and changed it's inheritance to UIScrollView. It works fine, but now I've got two sets of code that do exactly the same thing, just inherited from different parent classes. This makes keeping them both up to date a pain.

有没有更好的方法来做到这一点?

Is there a better way to do this?

推荐答案

单继承语言强制您使用委托.您可以将添加的功能分解为一个单独的类，您为派生类实例化该类，然后将派生类中的转发垫片写入实例.很痛苦.

Single inheritance languages force you to use delegation. You'd factor out the added functionality into a separate class that you instantiate for your derived classes and then write forwarding shims from the derived class to the instances. It's painful.

Objective C 有一些协议来描述添加的函数(任何未被覆盖的垫片)，然后如果你没有编写垫片，编译器就会出错……你仍然需要手动完成.

Objective C has protocols which would describe the added functions (any shims that are not overrides) and then the compiler would error-out if you didn't write the shim ... which you still have to do manually.

Objective C 也有允许您扩展现有类的类别，但这些类别不能共享(您必须单独扩展每个类)，因此它并没有真正的帮助.

Objective C also has categories that allow you to extend existing classes but these can't be shared (you have to extend each class individually) so it doesn't really help.

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