NSArray的大小和可变性 [英] NSArray size and mutability

问题描述

在Java中，我通常初始化是一个特定的大小，然后添加和更换对象作为我的code推移阵列。在Objective C，我不能这样做，有一个NSArray。我已经从Java移植往往超过code的使用NSMutableArray里，我以为比NSArray中表现较差efficent。 （我最好的猜测，如何存储的NSMutableArray它的成员是用链表，但我可能是错的）

In Java, I commonly initialize arrays that are a specific size and then add and replace objects as my code goes on. In Objective C, I can't do that with an NSArray. Code that I have ported over from Java often has to use NSMutableArray, which I assume perform less efficent than NSArray. (My best guess as to how NSMutableArray stores it's members is using a linked list, but I could be wrong)

有没有有固定的尺寸和允许阵列内的任何变化对各类目标C数组？为什么不能在与NSArray的某个对象来代替对象？我可以用C数组做到这一点，为什么不目标C？

Are there any types of arrays for Objective C that have fixed sizes and allow changes within the array? Why is it not possible to replace objects at a certain object with NSArray? I can do this with C arrays, why not Objective C?

推荐答案

您的假设是错误的，的NSMutableArray 将不会有任何比一个普通 NSArray的。

Your assumption is wrong, NSMutableArray won't be any slower than a plain NSArray.

的NSMutableArray 不打算使用一个链表，它会使用动态数组。这是每一位快，除了在需要的地方调整插入一个普通的数组。但是，由于这些指数得到进一步分开，其摊销到几乎相同，和相同的，如果你不打调整大小。

NSMutableArray is not going to use a linked list, it will use a dynamic array. It is every bit as fast as a plain array except on the insertions where it needs to resize. But since those get exponentially further apart, it amortizes to nearly the same, and identical if you don't hit a resize.

这是基本相同的Java的的ArrayList 。

It's basically the same as Java's ArrayList.

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