C++ 是否支持字符串类型的常量数组？
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Does C++ support constant arrays of type string?
提问by Alex
I'm a programming student in my first C++ class, and for a recent project I did, I was unable to create an array of strings like I could do in C#:
我是我的第一个 C++ 课程的编程学生，对于我最近做的一个项目，我无法像在 C# 中那样创建一个字符串数组：
string MONTHS[ARRAY_CAPACITY] = { "Jan", "Feb", "Mar", "April", "May", "June", "July", "Aug", "Sep", "Oct", "Nov", "Dec" };
// this yields many compiler errors in C++
Is it possible to do something similar in C++?
是否可以在 C++ 中做类似的事情？
Thanks!
谢谢！
回答by Mike Anchor
If you initialise the array in C++ then it doesn't require a size to be set (although it'll accept one), so:
如果您在 C++ 中初始化数组，则不需要设置大小（尽管它会接受一个），因此：
std::string months[] = { "Jan", "Feb", "Mar", "April", "May", "June", "July", "Aug", "Sep", "Oct", "Nov", "Dec" };
compiles fine with g++ for me and I'd expect it to compile elsewhere too. I expect your errors are due to the lack of std::namespace.
对我来说用 g++ 编译得很好，我希望它也能在其他地方编译。我希望您的错误是由于缺少std::命名空间。
回答by GManNickG
Yes, it does:
是的，它确实：
#include <string>
int main(void)
{
static const size_t Capacity = 12;
std::string Months[Capacity] = { "Jan", "Feb", "Mar", "April", "May",
"June", "July", "Aug", "Sep", "Oct",
"Nov", "Dec" };
}
Your errors were probably related to something else. Did you remember to use std::? Without knowing, it could be anything. Was Capacitythe wrong size? Etc.
您的错误可能与其他事情有关。你记得用过std::吗？在不知道的情况下，它可以是任何东西。是Capacity不是尺寸不对？等等。
Note your code wasn't actually a constant array. This is:
请注意，您的代码实际上并不是一个常量数组。这是：
#include <string>
int main(void)
{
static const size_t Capacity = 12;
static const std::string Months[Capacity] = { "Jan", "Feb", "Mar", "April",
/* ^^^^^^^^^^^^ */ "May", "June", "July", "Aug",
"Sep", "Oct", "Nov", "Dec" };
}
Also, you don't actually need Capacity, as others will show, and you coulduse const char*if you'd like, though you lose the std::stringinterface.
此外，您实际上并不需要Capacity，正如其他人会显示的那样，如果您愿意，您可以使用const char*，尽管您丢失了std::string界面。
回答by Collin Dauphinee
The preferred method for an array of constant strings would probably be an array of cstrings,
常量字符串数组的首选方法可能是一个 cstring 数组，
const char* MONTHS[] = { "Jan", "Feb", "Mar", "April", "May", "June", "July",
"Aug", "Sep", "Oct", "Nov", "Dec" };
However, it can also be done with std::strings,
然而，它也可以用 std::strings 来完成，
const string MONTHS[] = { string("Jan"), string("Feb"), ... };
Some compilers may not allow implicit conversion from char* to std::string when you initialize an array with curly braces; explicitly assigning an std::string constructed from a char* will fix that.
当您使用花括号初始化数组时，某些编译器可能不允许从 char* 隐式转换为 std::string；显式分配从 char* 构造的 std::string 将解决该问题。
回答by GenericMeatUnit
Yes, Visual C++ supports it - I've just done something similar. Not sure about other versions of C++.
是的，Visual C++ 支持它——我刚刚做了类似的事情。不确定其他版本的 C++。
Have you included the library? What is the definition of ARRAY_CAPACITY?
你包括图书馆吗？ARRAY_CAPACITY 的定义是什么？
When you say 'unable', do you mean you had compiler/linker errors or something else? Can you provide more details?
当您说“无法”时，您的意思是您遇到了编译器/链接器错误或其他问题？你能提供更多细节吗？
回答by AnT
Yes. The syntax you used in the question is correct, as long as the compiler understands that stringis std::stringand as long as the number of initializers in between {}does not exceed ARRAY_CAPACITY.
是的。你在提问中使用的语法是正确的，只要编译器理解string为std::string只要初始化中的数量{}不超过ARRAY_CAPACITY。
Of course, if you wanted to have a constantarray, as the title suggests, you should have declared it const. Without constyour array will have external linkage and cause linker errors if you put it into a header file included into multiple translation units.
当然，如果你想要一个常量数组，正如标题所暗示的那样，你应该声明它const。如果const您将数组放入包含在多个翻译单元中的头文件，则没有您的数组将具有外部链接并导致链接器错误。
const std::string MONTHS[ARRAY_CAPACITY] = { "Jan", /* and so on ... */ };
