在文件范围动态可变数组 [英] Variably modified array at file scope

问题描述

我想创建一个恒定的静态数组整个在我的.m文件的顶层类似这样的事情我的Objective-C实现文件中使用的：

I want to create a constant static array to be used throughout my Objective-C implementation file similar to something like this at the top level of my ".m" file:

static const int NUM_TYPES = 4;
static int types[NUM_TYPES] = { 
  1,
  2, 
  3, 
  4 };

我打算使用 NUM_TYPES 后在文件中，所以我希望把它放在一个变量。

I plan on using NUM_TYPES later on in the file so I wanted to put it in a variable.

然而，当我这样做，我得到的错误

However, when I do this, I get the error

动态可变类型文件范围

我推测，这可能是与数组的大小是一个变量（当我把一个整数字面那里，就像静态int型[4] ）。

I gather that this may have something to do with the array size being a variable (I don't get this message when I put an integer literal there, like static int types[4]).

我要解决这个问题，但也许我会对此都错了......我有2个目标位置：

I want to fix this, but maybe I am going about it all wrong...I have 2 goals here:

1. 要拥有一个数组，在整个文件
访问

2. 要封装 NUM_TYPES 为一个变量，所以我不具有相同的文字在我的文件散落不同的地方

1. To have an array which is accessible throughout the file
2. To encapsulate NUM_TYPES into a variable so I don't have the same literal scattered about different places in my file

有什么建议？

在C常见问题发现这个： http://c-faq.com/ansi/constasconst.html

推荐答案

这样做的原因警告是，<一个href=\"http://compgroups.net/comp.lang.c/Explanation-needed-for-const-int-error-variably-modified-at-file-scope\">const在C不等于常数。它的意思是只读。因此该值存储在内存中的地址，并有可能通过机code被改变。

The reason for this warning is that const in c doesn't mean constant. It means "read only". So the value is stored at a memory address and could potentially be changed by machine code.

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