blocks|key|11367|text|通常，当存在对数据进行操作的方法时，将使用类。如果只有数据，那么只需使用结构即可。似乎没有任何有用的方法来处理point或rect，所以不需要类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|11368|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Generally a class is used when there are methods that operate on the data. If you have data only then simply use a struct.
It seems there are not any useful methods to going along with point or rect so no need for a class.

blocks|key|4518976|text|每种编程范例都有其优缺点，面向对象编程(+object-oriented+programming，OOP)也不例外。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4518977|拥有类(即以面向对象的方式编写)的所有主要好处都是encapsulation、polymorphism和inheritance。|4518978|如果我们声明像Rect或Point这样的简单单元，我们将不会使用该列表中的任何东西，但我们将带来OOP的所有缺点，包括隐式可变、更复杂的内存管理、指针引用、隐式actors、断开的封装(使用setter/getter)等。我不会在这里列出OOP中确实存在的数百个anti-patterns。|4518979|我怀疑为Cocoa中的Rect和Point选择结构是否有C遗留的合理性，首先是因为Objective-C从一开始就支持类，其次是因为全新的Swift语言没有这种遗留，但几乎所有的标准类型和容器都在其标准库中声明为结构，而不是类。|4518980|一般来说，如果你不需要封装、多态性和继承--你应该考虑将你的新实体声明为一个结构，并尽可能避免OOP。|4518981|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/Object-oriented_programming|1|https://en.wikipedia.org/wiki/Encapsulation_%2528object-oriented_programming%2529|2|https://en.wikipedia.org/wiki/Polymorphism_%2528computer_science%2529|3|https://en.wikipedia.org/wiki/Inheritance_%2528object-oriented_programming%2529|4|https://en.wikipedia.org/wiki/Anti-pattern|5|https://en.wikipedia.org/wiki/Swift_%2528Apple_programming_language%2529^0|L|R|0|0|P|D|1|13|C|2|1G|B|3|0|3N|D|4|0|1X|5|5|0|0^^$0|@$1|2|3|4|5|6|7|13|8|@]|9|@$A|14|B|15|1|16]]|C|$]]|$1|D|3|E|5|6|7|17|8|@]|9|@$A|18|B|19|1|1A]|$A|1B|B|1C|1|1D]|$A|1E|B|1F|1|1G]]|C|$]]|$1|F|3|G|5|6|7|1H|8|@]|9|@$A|1I|B|1J|1|1K]]|C|$]]|$1|H|3|I|5|6|7|1L|8|@]|9|@$A|1M|B|1N|1|1O]]|C|$]]|$1|J|3|K|5|6|7|1P|8|@]|9|@]|C|$]]|$1|L|3|-4|5|6|7|1Q|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]|T|$5|O|P|Q|C|$R|U]]|V|$5|O|P|Q|C|$R|W]]|X|$5|O|P|Q|C|$R|Y]]|Z|$5|O|P|Q|C|$R|10]]|11|$5|O|P|Q|C|$R|12]]]]

Each programming paradigm has its own pros and cons, and <a href="https://en.wikipedia.org/wiki/Object-oriented_programming">object-oriented programming</a> (OOP) in not an exception.

All major benefits from having classes (that is, writing in an object-oriented style) is <a href="https://en.wikipedia.org/wiki/Encapsulation_%28object-oriented_programming%29">encapsulation</a>, <a href="https://en.wikipedia.org/wiki/Polymorphism_%28computer_science%29">polymorphism</a> and <a href="https://en.wikipedia.org/wiki/Inheritance_%28object-oriented_programming%29">inheritance</a>.

If we declare such simple units as Rect or Point a class, we won't use anything from that list, but we'll bring all the disadvantages that OOP has, including implicit mutability, more complex memory management, pointer references, implicit actors, broken encapsulation (with setters/getters), etc. And I don't list here hundreds of <a href="https://en.wikipedia.org/wiki/Anti-pattern">anti-patterns</a> that do exist in OOP.

I doubt that the choice of structs for Rect and Point in Cocoa was justified by C legacy, first of all because Objective-C supported classes from the outset, and secondly because the brand new <a href="https://en.wikipedia.org/wiki/Swift_%28Apple_programming_language%29">Swift</a> language does not have this legacy, but still almost all standard types and containers are declared in its standard library as structures, not classes.

In general, if you don't need encapsulation, polymorphism and inheritance - you should consider declaring your new entity as a struct and avoid OOP whenever possible.

blocks|key|4519024|text|我认为这与这样一个事实有关:每个结构都包含原始类型的数据(一般是浮点数和双精度数)，而没有自己的任何操作(如函数或方法)，因此不需要更复杂的东西，如全功能类(不需要导入，也不需要样板代码)。初始化器)，当然，正如其他同事所提到的，因为Objective-C是C的超集。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4519025|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I believe it has to do with the fact that each struct holds primitive types of data (in general floats and doubles) without any actions on their own (like functions or methods) so there was no need for something more complex like a fully featured class (no imports and no boilerplate code eg. initializers) and of course, as other colleagues mentioned, because Objective-C is a superset of C.

blocks|key|4519062|text|如果你已经使用Objective-C有一段时间了，那么你就会知道它是coreFoundation之上的一个OOP层，它是所有的结构和‘不透明类型’(带有秘密的结构)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4519063|例如，NSDictionary实际上只是CFtype+CFDictionaryRef的包装器。好吧，你在这里询问的东西，大小，点，rect，edgeInsets，等等，只是被确定为不保证升级的小数据类型。基本类型(int、double、bool等)也没有得到免费的桥的(公共)类。他们得到了NSNumber集群，这些人都被捆绑在NSValue包装器中。如果需要，您可以编写一个具体的类来包装一个特定的类。|4519064|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

If you've been playing with Objective-C for a while then you'll know that it is an OOP layer on top of coreFoundation, which is all structs and 'opaque types' (structs with secrets)..

For example, NSDictionary is really just a wrapper around the CFtype, CFDictionaryRef. Well, the things you're asking about here, size, point, rect, edgeInsets, etc. are just little data types which were determined to not warrant the upgrade. Primitives (int, double, bool, etc.) didn't get a (public) class to toll free bridge either. They got the NSNumber cluster, and these guys all got bunched together in the NSValue wrapper. You can write a concrete class to wrap a specific one if you need to...

blocks|key|11504|text|当您想要按值传递事物时，您可以使用结构；当您想要按引用传递时，您可以使用类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|11505|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You use structs when you want to pass things by value and classes when you want to pass them by reference.

blocks|key|11514|text|还有一个优点是运算速度。这些点和矩形主要用来渲染一些东西，因此需要比以往更快的操作。而不是分配一个对象，这将触发递归init，花费大量字节和cpu周期进行卧底工作，它只是更快地说“这里我有16个字节，这是2个CGFloats+of+NSPoint结构”。当将工作委托给GPU时，这也是很有意义的，因为GPU对OOP和对象的方法一无所知，但需要在屏幕上绘制大量内容而不会出现故障。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|11515|entityMap^0|1M|4|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Also a good point is operation speed. These points and rects are mostly used to render something and thus need faster operating than ever. Instead of allocating an object, which will trigger recursive <code>init</code>, spending a lot of bytes and cpu cycles for undercover work, it's just faster to say "here I have 16 bytes which is 2 CGFloats of NSPoint struct". This also makes a lot of sence when delegating work to a GPU, which don't know anything about OOP and methods of your objects, but need to draw a lot on screen without glitches.

blocks|key|11542|text|压倒一切的原因是性能--Cocoa的所有性能关键型API(图形、音频)都倾向于使用C结构和函数来实现这类目的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|11543|原因是C编译器可以更容易地对它们进行优化。C函数的调用成本比方法更低，而且它们可以由编译器自动内联，从而完全消除了函数调用开销。C结构是在堆栈而不是堆上分配的，这意味着处理主要可以在寄存器或低级CPU缓存中完成，而不是调用主内存，后者要慢数百倍。|11544|Cocoa方法是动态调度的。它们可能会被子类或swizzling覆盖，因此编译器不能内联它们，因为直到它们在运行时执行时，编译器才能确定它们将做什么。Cocoa类是在堆上分配的，所以它们必须被分配/释放，还有所有其他的开销，比如引用计数。它们也可能最终散布在内存中，这意味着由于它们所在的内存块必须分页进出缓存，因此可能会有显著的性能损失。|11545|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

The overriding reason is performance - all of Cocoa's performance-critical APIs (graphics, audio) tend to use C structs and functions for this sort of purpose.

The reasons are that these can much more easily be optimised by the C-compiler. C functions can be called more cheaply than methods, and they can be inlined automatically by the compiler, removing the function call overhead altogether. C structs are allocated on the stack instead of the heap, which means that processing can mostly be done in registers or low-level CPU caches instead of calling out to main memory, which is hundreds of times slower.

Cocoa methods are dynamically dispatched. They might be overridden by a subclass or swizzling, so the compiler cannot inline them because it can't be sure what they will do until they are executed at runtime. Cocoa classes are allocated on the heap, so they must be allocated/deallocated, and there's all the other overhead such as reference counting. They are also likely to end up spread out in memory, which means that there may be significant performance losses due to the memory blocks they reside in having to be paged in and out of cache.

I've recently needed to create my own type similar to NSRect that has an anchor point (essentially an NSRect with another NSPoint in it).

After <a href="https://stackoverflow.com/questions/2567205/objective-c-class-or-struct">some</a> <a href="https://stackoverflow.com/questions/6530481/struct-or-class">research</a> I found that I was actually probably better off to just make this a class (as in NSObject subclass), rather than using struct. Why then has Apple make these types structs, not classes? It seems like it would have many benefits, such as not having to wrap them in NSValues, not have to use C functions to interact with them, etc.

I'm sure they'd have a reason. Is it simply the slightly less memory usage? Is it just historical? Or have I missed something bigger?

Why are NSRect, NSPoint, etc. structs, not classes?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我最近需要创建我自己的类似于NSRect的类型，它有一个锚点(本质上是一个带有另一个NSPoint的NSRect )。在使用 之后，我发现实际上将其作为一个类(就像在NSObject子类中一样)可能比使用结构更好。那么为什么Apple要做这些类型的结构，而不是类呢？它似乎有很多好处，比如不必将它们包装在NSValues...

问为什么NSRect、NSPoint等是结构，而不是类？
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问为什么NSRect、NSPoint等是结构，而不是类？EN