在NSArray中放置c-struct的最好方法是什么？ [英] What's the best way to put a c-struct in an NSArray?

问题描述

在 NSArray 中存储c结构的常用方法是什么？优点，缺点，内存处理？

What's the usual way to store c-structures in an NSArray? Advantages, disadvantages, memory handling?

值得注意的是， valueWithBytes 和 valueWithPointer

Notably, what's the difference between valueWithBytes and valueWithPointer -- raised by justin and catfish below.

这里有一个链接到苹果讨论的 valueWithBytes：objCType： / code>为未来的读者...

Here's a link to Apple's discussion of valueWithBytes:objCType: for future readers...

对于一些横向思维和更多的性能，Evgen提出了使用

For some lateral thinking and looking more at performance, Evgen has raised the issue of using STL::vector in C++.

（这引发了一个有趣的问题：是否有快速c库，不像 STL :: vector ，但是要轻得多，允许最小的整齐处理数组...？）

(That raises an interesting issue: is there a fast c library, not unlike STL::vector but much much lighter, that allows for the minimal "tidy handling of arrays" ...?)

所以原来的问题...

So the original question...

例如：

typedef struct _Megapoint {
    float   w,x,y,z;
} Megapoint;

所以：什么是正常的，最好的，惯用的方式来存储自己的结构， c $ c> NSArray ，以及如何处理该成语中的内存？

So: what's the normal, best, idiomatic way to store one's own structure like that in an NSArray, and how do you handle memory in that idiom?

请注意，我专门寻找常用的成语存储结构。当然，通过做一个新的小类可以避免这个问题。然而，我想知道如何通常的成语，实际上将结构体放在数组中，感谢。

Please note that I am specifically looking for the usual idiom to store structs. Of course, one could avoid the issue by making a new little class. However I want to know how the usual idiom for actually putting structs in an array, thanks.

这里的NSData方法可能是？不是最好的...

BTW here's the NSData approach which is perhaps? not best...

Megapoint p;
NSArray *a = [NSArray arrayWithObjects:
    [NSData dataWithBytes:&p length:sizeof(Megapoint)],
    [NSData dataWithBytes:&p length:sizeof(Megapoint)],
    [NSData dataWithBytes:&p length:sizeof(Megapoint)],
        nil];

BTW作为参考，感谢Jarret Hardie，下面介绍如何存储 CGPoints 和 NSArray 中类似：

BTW as a point of reference and thanks to Jarret Hardie, here's how to store CGPoints and similar in an NSArray:

NSArray *points = [NSArray arrayWithObjects:
        [NSValue valueWithCGPoint:CGPointMake(6.9, 6.9)],
        [NSValue valueWithCGPoint:CGPointMake(6.9, 6.9)],
        nil];

（请参阅）

(see How can I add CGPoint objects to an NSArray the easy way?)

推荐答案

NSValue 不仅支持CoreGraphics结构 - 你也可以使用它。我建议这样做，因为类可能比 NSData 更轻的重量为简单的数据结构。

NSValue doesn't only support CoreGraphics structures – you can use it for your own too. I would recommend doing so, as the class is probably lighter weight than NSData for simple data structures.

一个表达式如下：

[NSValue valueWithBytes:&p objCType:@encode(Megapoint)];

重新输入值：

Megapoint p;
[value getValue:&p];

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